urllib.request — M2Crypto documentation

# Source code for urllib.request

    """An extensible library for opening URLs using a variety of protocols

    The simplest way to use this module is to call the urlopen function,
    which accepts a string containing a URL or a Request object (described
    below).  It opens the URL and returns the results as file-like
    object; the returned object has some extra methods described below.

    The OpenerDirector manages a collection of Handler objects that do
    all the actual work.  Each Handler implements a particular protocol or
    option.  The OpenerDirector is a composite object that invokes the
    Handlers needed to open the requested URL.  For example, the
    HTTPHandler performs HTTP GET and POST requests and deals with
    non-error returns.  The HTTPRedirectHandler automatically deals with
    HTTP 301, 302, 303 and 307 redirect errors, and the HTTPDigestAuthHandler
    deals with digest authentication.

    urlopen(url, data=None) -- Basic usage is the same as original
    urllib.  pass the url and optionally data to post to an HTTP URL, and
    get a file-like object back.  One difference is that you can also pass
    a Request instance instead of URL.  Raises a URLError (subclass of
    OSError); for HTTP errors, raises an HTTPError, which can also be
    treated as a valid response.

    build_opener -- Function that creates a new OpenerDirector instance.
    Will install the default handlers.  Accepts one or more Handlers as
    arguments, either instances or Handler classes that it will
    instantiate.  If one of the argument is a subclass of the default
    handler, the argument will be installed instead of the default.

    install_opener -- Installs a new opener as the default opener.

    objects of interest:

    OpenerDirector -- Sets up the User Agent as the Python-urllib client and manages
    the Handler classes, while dealing with requests and responses.

    Request -- An object that encapsulates the state of a request.  The
    state can be as simple as the URL.  It can also include extra HTTP
    headers, e.g. a User-Agent.

    BaseHandler --

    internals:
    BaseHandler and parent
    _call_chain conventions

    Example usage:

    import urllib.request

    # set up authentication info
    authinfo = urllib.request.HTTPBasicAuthHandler()
    authinfo.add_password(realm='PDQ Application',
                          uri='https://mahler:8092/site-updates.py',
                          user='klem',
                          passwd='geheim$parole')

    proxy_support = urllib.request.ProxyHandler({"http" : "http://ahad-haam:3128"})

    # build a new opener that adds authentication and caching FTP handlers
    opener = urllib.request.build_opener(proxy_support, authinfo,
                                         urllib.request.CacheFTPHandler)

    # install it
    urllib.request.install_opener(opener)

    f = urllib.request.urlopen('http://www.python.org/')
    """

    # XXX issues:
    # If an authentication error handler that tries to perform
    # authentication for some reason but fails, how should the error be
    # signalled?  The client needs to know the HTTP error code.  But if
    # the handler knows that the problem was, e.g., that it didn't know
    # that hash algo that requested in the challenge, it would be good to
    # pass that information along to the client, too.
    # ftp errors aren't handled cleanly
    # check digest against correct (i.e. non-apache) implementation

    # Possible extensions:
    # complex proxies  XXX not sure what exactly was meant by this
    # abstract factory for opener

    import base64
    import bisect
    import email
    import hashlib
    import http.client
    import io
    import os
    import posixpath
    import re
    import socket
    import string
    import sys
    import time
    import tempfile
    import contextlib
    import warnings

    from urllib.error import URLError, HTTPError, ContentTooShortError
    from urllib.parse import (
        urlparse, urlsplit, urljoin, unwrap, quote, unquote,
        _splittype, _splithost, _splitport, _splituser, _splitpasswd,
        _splitattr, _splitquery, _splitvalue, _splittag, _to_bytes,
        unquote_to_bytes, urlunparse)
    from urllib.response import addinfourl, addclosehook

    # check for SSL
    try:
        import ssl
    except ImportError:
        _have_ssl = False
    else:
        _have_ssl = True

    __all__ = [
        # Classes
        'Request', 'OpenerDirector', 'BaseHandler', 'HTTPDefaultErrorHandler',
        'HTTPRedirectHandler', 'HTTPCookieProcessor', 'ProxyHandler',
        'HTTPPasswordMgr', 'HTTPPasswordMgrWithDefaultRealm',
        'HTTPPasswordMgrWithPriorAuth', 'AbstractBasicAuthHandler',
        'HTTPBasicAuthHandler', 'ProxyBasicAuthHandler', 'AbstractDigestAuthHandler',
        'HTTPDigestAuthHandler', 'ProxyDigestAuthHandler', 'HTTPHandler',
        'FileHandler', 'FTPHandler', 'CacheFTPHandler', 'DataHandler',
        'UnknownHandler', 'HTTPErrorProcessor',
        # Functions
        'urlopen', 'install_opener', 'build_opener',
        'pathname2url', 'url2pathname', 'getproxies',
        # Legacy interface
        'urlretrieve', 'urlcleanup', 'URLopener', 'FancyURLopener',
    ]

    # used in User-Agent header sent
    __version__ = '%d.%d' % sys.version_info[:2]

    _opener = None
    def urlopen(url, data=None, timeout=socket._GLOBAL_DEFAULT_TIMEOUT,
                *, cafile=None, capath=None, cadefault=False, context=None):
        '''Open the URL url, which can be either a string or a Request object.

        *data* must be an object specifying additional data to be sent to
        the server, or None if no such data is needed.  See Request for
        details.

        urllib.request module uses HTTP/1.1 and includes a "Connection:close"
        header in its HTTP requests.

        The optional *timeout* parameter specifies a timeout in seconds for
        blocking operations like the connection attempt (if not specified, the
        global default timeout setting will be used). This only works for HTTP,
        HTTPS and FTP connections.

        If *context* is specified, it must be a ssl.SSLContext instance describing
        the various SSL options. See HTTPSConnection for more details.

        The optional *cafile* and *capath* parameters specify a set of trusted CA
        certificates for HTTPS requests. cafile should point to a single file
        containing a bundle of CA certificates, whereas capath should point to a
        directory of hashed certificate files. More information can be found in
        ssl.SSLContext.load_verify_locations().

        The *cadefault* parameter is ignored.

        This function always returns an object which can work as a context
        manager and has methods such as

        * geturl() - return the URL of the resource retrieved, commonly used to
          determine if a redirect was followed

        * info() - return the meta-information of the page, such as headers, in the
          form of an email.message_from_string() instance (see Quick Reference to
          HTTP Headers)

        * getcode() - return the HTTP status code of the response.  Raises URLError
          on errors.

        For HTTP and HTTPS URLs, this function returns a http.client.HTTPResponse
        object slightly modified. In addition to the three new methods above, the
        msg attribute contains the same information as the reason attribute ---
        the reason phrase returned by the server --- instead of the response
        headers as it is specified in the documentation for HTTPResponse.

        For FTP, file, and data URLs and requests explicitly handled by legacy
        URLopener and FancyURLopener classes, this function returns a
        urllib.response.addinfourl object.

        Note that None may be returned if no handler handles the request (though
        the default installed global OpenerDirector uses UnknownHandler to ensure
        this never happens).

        In addition, if proxy settings are detected (for example, when a *_proxy
        environment variable like http_proxy is set), ProxyHandler is default
        installed and makes sure the requests are handled through the proxy.

        '''
        global _opener
        if cafile or capath or cadefault:
            import warnings
            warnings.warn("cafile, capath and cadefault are deprecated, use a "
                          "custom context instead.", DeprecationWarning, 2)
            if context is not None:
                raise ValueError(
                    "You can't pass both context and any of cafile, capath, and "
                    "cadefault"
                )
            if not _have_ssl:
                raise ValueError('SSL support not available')
            context = ssl.create_default_context(ssl.Purpose.SERVER_AUTH,
                                                 cafile=cafile,
                                                 capath=capath)
            https_handler = HTTPSHandler(context=context)
            opener = build_opener(https_handler)
        elif context:
            https_handler = HTTPSHandler(context=context)
            opener = build_opener(https_handler)
        elif _opener is None:
            _opener = opener = build_opener()
        else:
            opener = _opener
        return opener.open(url, data, timeout)

    def install_opener(opener):
        global _opener
        _opener = opener

    _url_tempfiles = []
    def urlretrieve(url, filename=None, reporthook=None, data=None):
        """
        Retrieve a URL into a temporary location on disk.

        Requires a URL argument. If a filename is passed, it is used as
        the temporary file location. The reporthook argument should be
        a callable that accepts a block number, a read size, and the
        total file size of the URL target. The data argument should be
        valid URL encoded data.

        If a filename is passed and the URL points to a local resource,
        the result is a copy from local file to new file.

        Returns a tuple containing the path to the newly created
        data file as well as the resulting HTTPMessage object.
        """
        url_type, path = _splittype(url)

        with contextlib.closing(urlopen(url, data)) as fp:
            headers = fp.info()

            # Just return the local path and the "headers" for file://
            # URLs. No sense in performing a copy unless requested.
            if url_type == "file" and not filename:
                return os.path.normpath(path), headers

            # Handle temporary file setup.
            if filename:
                tfp = open(filename, 'wb')
            else:
                tfp = tempfile.NamedTemporaryFile(delete=False)
                filename = tfp.name
                _url_tempfiles.append(filename)

            with tfp:
                result = filename, headers
                bs = 1024*8
                size = -1
                read = 0
                blocknum = 0
                if "content-length" in headers:
                    size = int(headers["Content-Length"])

                if reporthook:
                    reporthook(blocknum, bs, size)

                while True:
                    block = fp.read(bs)
                    if not block:
                        break
                    read += len(block)
                    tfp.write(block)
                    blocknum += 1
                    if reporthook:
                        reporthook(blocknum, bs, size)

        if size >= 0 and read < size:
            raise ContentTooShortError(
                "retrieval incomplete: got only %i out of %i bytes"
                % (read, size), result)

        return result

    def urlcleanup():
        """Clean up temporary files from urlretrieve calls."""
        for temp_file in _url_tempfiles:
            try:
                os.unlink(temp_file)
            except OSError:
                pass

        del _url_tempfiles[:]
        global _opener
        if _opener:
            _opener = None

    # copied from cookielib.py
    _cut_port_re = re.compile(r":\d+$", re.ASCII)
    def request_host(request):
        """Return request-host, as defined by RFC 2965.

        Variation from RFC: returned value is lowercased, for convenient
        comparison.

        """
        url = request.full_url
        host = urlparse(url)[1]
        if host == "":
            host = request.get_header("Host", "")

        # remove port, if present
        host = _cut_port_re.sub("", host, 1)
        return host.lower()

    class Request:

        def __init__(self, url, data=None, headers={},
                     origin_req_host=None, unverifiable=False,
                     method=None):
            self.full_url = url
            self.headers = {}
            self.unredirected_hdrs = {}
            self._data = None
            self.data = data
            self._tunnel_host = None
            for key, value in headers.items():
                self.add_header(key, value)
            if origin_req_host is None:
                origin_req_host = request_host(self)
            self.origin_req_host = origin_req_host
            self.unverifiable = unverifiable
            if method:
                self.method = method

        @property
        def full_url(self):
            if self.fragment:
                return '{}#{}'.format(self._full_url, self.fragment)
            return self._full_url

        @full_url.setter
        def full_url(self, url):
            # unwrap('<URL:type://host/path>') --> 'type://host/path'
            self._full_url = unwrap(url)
            self._full_url, self.fragment = _splittag(self._full_url)
            self._parse()

        @full_url.deleter
        def full_url(self):
            self._full_url = None
            self.fragment = None
            self.selector = ''

        @property
        def data(self):
            return self._data

        @data.setter
        def data(self, data):
            if data != self._data:
                self._data = data
                # issue 16464
                # if we change data we need to remove content-length header
                # (cause it's most probably calculated for previous value)
                if self.has_header("Content-length"):
                    self.remove_header("Content-length")

        @data.deleter
        def data(self):
            self.data = None

        def _parse(self):
            self.type, rest = _splittype(self._full_url)
            if self.type is None:
                raise ValueError("unknown url type: %r" % self.full_url)
            self.host, self.selector = _splithost(rest)
            if self.host:
                self.host = unquote(self.host)

        def get_method(self):
            """Return a string indicating the HTTP request method."""
            default_method = "POST" if self.data is not None else "GET"
            return getattr(self, 'method', default_method)

        def get_full_url(self):
            return self.full_url

        def set_proxy(self, host, type):
            if self.type == 'https' and not self._tunnel_host:
                self._tunnel_host = self.host
            else:
                self.type= type
                self.selector = self.full_url
            self.host = host

        def has_proxy(self):
            return self.selector == self.full_url

        def add_header(self, key, val):
            # useful for something like authentication
            self.headers[key.capitalize()] = val

        def add_unredirected_header(self, key, val):
            # will not be added to a redirected request
            self.unredirected_hdrs[key.capitalize()] = val

        def has_header(self, header_name):
            return (header_name in self.headers or
                    header_name in self.unredirected_hdrs)

        def get_header(self, header_name, default=None):
            return self.headers.get(
                header_name,
                self.unredirected_hdrs.get(header_name, default))

        def remove_header(self, header_name):
            self.headers.pop(header_name, None)
            self.unredirected_hdrs.pop(header_name, None)

        def header_items(self):
            hdrs = {**self.unredirected_hdrs, **self.headers}
            return list(hdrs.items())

    class OpenerDirector:
        def __init__(self):
            client_version = "Python-urllib/%s" % __version__
            self.addheaders = [('User-agent', client_version)]
            # self.handlers is retained only for backward compatibility
            self.handlers = []
            # manage the individual handlers
            self.handle_open = {}
            self.handle_error = {}
            self.process_response = {}
            self.process_request = {}

        def add_handler(self, handler):
            if not hasattr(handler, "add_parent"):
                raise TypeError("expected BaseHandler instance, got %r" %
                                type(handler))

            added = False
            for meth in dir(handler):
                if meth in ["redirect_request", "do_open", "proxy_open"]:
                    # oops, coincidental match
                    continue

                i = meth.find("_")
                protocol = meth[:i]
                condition = meth[i+1:]

                if condition.startswith("error"):
                    j = condition.find("_") + i + 1
                    kind = meth[j+1:]
                    try:
                        kind = int(kind)
                    except ValueError:
                        pass
                    lookup = self.handle_error.get(protocol, {})
                    self.handle_error[protocol] = lookup
                elif condition == "open":
                    kind = protocol
                    lookup = self.handle_open
                elif condition == "response":
                    kind = protocol
                    lookup = self.process_response
                elif condition == "request":
                    kind = protocol
                    lookup = self.process_request
                else:
                    continue

                handlers = lookup.setdefault(kind, [])
                if handlers:
                    bisect.insort(handlers, handler)
                else:
                    handlers.append(handler)
                added = True

            if added:
                bisect.insort(self.handlers, handler)
                handler.add_parent(self)

        def close(self):
            # Only exists for backwards compatibility.
            pass

        def _call_chain(self, chain, kind, meth_name, *args):
            # Handlers raise an exception if no one else should try to handle
            # the request, or return None if they can't but another handler
            # could.  Otherwise, they return the response.
            handlers = chain.get(kind, ())
            for handler in handlers:
                func = getattr(handler, meth_name)
                result = func(*args)
                if result is not None:
                    return result

        def open(self, fullurl, data=None, timeout=socket._GLOBAL_DEFAULT_TIMEOUT):
            # accept a URL or a Request object
            if isinstance(fullurl, str):
                req = Request(fullurl, data)
            else:
                req = fullurl
                if data is not None:
                    req.data = data

            req.timeout = timeout
            protocol = req.type

            # pre-process request
            meth_name = protocol+"_request"
            for processor in self.process_request.get(protocol, []):
                meth = getattr(processor, meth_name)
                req = meth(req)

            sys.audit('urllib.Request', req.full_url, req.data, req.headers, req.get_method())
            response = self._open(req, data)

            # post-process response
            meth_name = protocol+"_response"
            for processor in self.process_response.get(protocol, []):
                meth = getattr(processor, meth_name)
                response = meth(req, response)

            return response

        def _open(self, req, data=None):
            result = self._call_chain(self.handle_open, 'default',
                                      'default_open', req)
            if result:
                return result

            protocol = req.type
            result = self._call_chain(self.handle_open, protocol, protocol +
                                      '_open', req)
            if result:
                return result

            return self._call_chain(self.handle_open, 'unknown',
                                    'unknown_open', req)

        def error(self, proto, *args):
            if proto in ('http', 'https'):
                # XXX http[s] protocols are special-cased
                dict = self.handle_error['http'] # https is not different than http
                proto = args[2]  # YUCK!
                meth_name = 'http_error_%s' % proto
                http_err = 1
                orig_args = args
            else:
                dict = self.handle_error
                meth_name = proto + '_error'
                http_err = 0
            args = (dict, proto, meth_name) + args
            result = self._call_chain(*args)
            if result:
                return result

            if http_err:
                args = (dict, 'default', 'http_error_default') + orig_args
                return self._call_chain(*args)

    # XXX probably also want an abstract factory that knows when it makes
    # sense to skip a superclass in favor of a subclass and when it might
    # make sense to include both

    def build_opener(*handlers):
        """Create an opener object from a list of handlers.

        The opener will use several default handlers, including support
        for HTTP, FTP and when applicable HTTPS.

        If any of the handlers passed as arguments are subclasses of the
        default handlers, the default handlers will not be used.
        """
        opener = OpenerDirector()
        default_classes = [ProxyHandler, UnknownHandler, HTTPHandler,
                           HTTPDefaultErrorHandler, HTTPRedirectHandler,
                           FTPHandler, FileHandler, HTTPErrorProcessor,
                           DataHandler]
        if hasattr(http.client, "HTTPSConnection"):
            default_classes.append(HTTPSHandler)
        skip = set()
        for klass in default_classes:
            for check in handlers:
                if isinstance(check, type):
                    if issubclass(check, klass):
                        skip.add(klass)
                elif isinstance(check, klass):
                    skip.add(klass)
        for klass in skip:
            default_classes.remove(klass)

        for klass in default_classes:
            opener.add_handler(klass())

        for h in handlers:
            if isinstance(h, type):
                h = h()
            opener.add_handler(h)
        return opener

    class BaseHandler:
        handler_order = 500

        def add_parent(self, parent):
            self.parent = parent

        def close(self):
            # Only exists for backwards compatibility
            pass

        def __lt__(self, other):
            if not hasattr(other, "handler_order"):
                # Try to preserve the old behavior of having custom classes
                # inserted after default ones (works only for custom user
                # classes which are not aware of handler_order).
                return True
            return self.handler_order < other.handler_order

    class HTTPErrorProcessor(BaseHandler):
        """Process HTTP error responses."""
        handler_order = 1000  # after all other processing

        def http_response(self, request, response):
            code, msg, hdrs = response.code, response.msg, response.info()

            # According to RFC 2616, "2xx" code indicates that the client's
            # request was successfully received, understood, and accepted.
            if not (200 <= code < 300):
                response = self.parent.error(
                    'http', request, response, code, msg, hdrs)

            return response

        https_response = http_response

    class HTTPDefaultErrorHandler(BaseHandler):
        def http_error_default(self, req, fp, code, msg, hdrs):
            raise HTTPError(req.full_url, code, msg, hdrs, fp)

    class HTTPRedirectHandler(BaseHandler):
        # maximum number of redirections to any single URL
        # this is needed because of the state that cookies introduce
        max_repeats = 4
        # maximum total number of redirections (regardless of URL) before
        # assuming we're in a loop
        max_redirections = 10

        def redirect_request(self, req, fp, code, msg, headers, newurl):
            """Return a Request or None in response to a redirect.

            This is called by the http_error_30x methods when a
            redirection response is received.  If a redirection should
            take place, return a new Request to allow http_error_30x to
            perform the redirect.  Otherwise, raise HTTPError if no-one
            else should try to handle this url.  Return None if you can't
            but another Handler might.
            """
            m = req.get_method()
            if (not (code in (301, 302, 303, 307) and m in ("GET", "HEAD")
                or code in (301, 302, 303) and m == "POST")):
                raise HTTPError(req.full_url, code, msg, headers, fp)

            # Strictly (according to RFC 2616), 301 or 302 in response to
            # a POST MUST NOT cause a redirection without confirmation
            # from the user (of urllib.request, in this case).  In practice,
            # essentially all clients do redirect in this case, so we do
            # the same.

            # Be conciliant with URIs containing a space.  This is mainly
            # redundant with the more complete encoding done in http_error_302(),
            # but it is kept for compatibility with other callers.
            newurl = newurl.replace(' ', '%20')

            CONTENT_HEADERS = ("content-length", "content-type")
            newheaders = {k: v for k, v in req.headers.items()
                          if k.lower() not in CONTENT_HEADERS}
            return Request(newurl,
                           headers=newheaders,
                           origin_req_host=req.origin_req_host,
                           unverifiable=True)

        # Implementation note: To avoid the server sending us into an
        # infinite loop, the request object needs to track what URLs we
        # have already seen.  Do this by adding a handler-specific
        # attribute to the Request object.
        def http_error_302(self, req, fp, code, msg, headers):
            # Some servers (incorrectly) return multiple Location headers
            # (so probably same goes for URI).  Use first header.
            if "location" in headers:
                newurl = headers["location"]
            elif "uri" in headers:
                newurl = headers["uri"]
            else:
                return

            # fix a possible malformed URL
            urlparts = urlparse(newurl)

            # For security reasons we don't allow redirection to anything other
            # than http, https or ftp.

            if urlparts.scheme not in ('http', 'https', 'ftp', ''):
                raise HTTPError(
                    newurl, code,
                    "%s - Redirection to url '%s' is not allowed" % (msg, newurl),
                    headers, fp)

            if not urlparts.path and urlparts.netloc:
                urlparts = list(urlparts)
                urlparts[2] = "/"
            newurl = urlunparse(urlparts)

            # http.client.parse_headers() decodes as ISO-8859-1.  Recover the
            # original bytes and percent-encode non-ASCII bytes, and any special
            # characters such as the space.
            newurl = quote(
                newurl, encoding="iso-8859-1", safe=string.punctuation)
            newurl = urljoin(req.full_url, newurl)

            # XXX Probably want to forget about the state of the current
            # request, although that might interact poorly with other
            # handlers that also use handler-specific request attributes
            new = self.redirect_request(req, fp, code, msg, headers, newurl)
            if new is None:
                return

            # loop detection
            # .redirect_dict has a key url if url was previously visited.
            if hasattr(req, 'redirect_dict'):
                visited = new.redirect_dict = req.redirect_dict
                if (visited.get(newurl, 0) >= self.max_repeats or
                    len(visited) >= self.max_redirections):
                    raise HTTPError(req.full_url, code,
                                    self.inf_msg + msg, headers, fp)
            else:
                visited = new.redirect_dict = req.redirect_dict = {}
            visited[newurl] = visited.get(newurl, 0) + 1

            # Don't close the fp until we are sure that we won't use it
            # with HTTPError.
            fp.read()
            fp.close()

            return self.parent.open(new, timeout=req.timeout)

        http_error_301 = http_error_303 = http_error_307 = http_error_302

        inf_msg = "The HTTP server returned a redirect error that would " \
                  "lead to an infinite loop.\n" \
                  "The last 30x error message was:\n"

    def _parse_proxy(proxy):
        """Return (scheme, user, password, host/port) given a URL or an authority.

        If a URL is supplied, it must have an authority (host:port) component.
        According to RFC 3986, having an authority component means the URL must
        have two slashes after the scheme.
        """
        scheme, r_scheme = _splittype(proxy)
        if not r_scheme.startswith("/"):
            # authority
            scheme = None
            authority = proxy
        else:
            # URL
            if not r_scheme.startswith("//"):
                raise ValueError("proxy URL with no authority: %r" % proxy)
            # We have an authority, so for RFC 3986-compliant URLs (by ss 3.
            # and 3.3.), path is empty or starts with '/'
            end = r_scheme.find("/", 2)
            if end == -1:
                end = None
            authority = r_scheme[2:end]
        userinfo, hostport = _splituser(authority)
        if userinfo is not None:
            user, password = _splitpasswd(userinfo)
        else:
            user = password = None
        return scheme, user, password, hostport

    class ProxyHandler(BaseHandler):
        # Proxies must be in front
        handler_order = 100

        def __init__(self, proxies=None):
            if proxies is None:
                proxies = getproxies()
            assert hasattr(proxies, 'keys'), "proxies must be a mapping"
            self.proxies = proxies
            for type, url in proxies.items():
                type = type.lower()
                setattr(self, '%s_open' % type,
                        lambda r, proxy=url, type=type, meth=self.proxy_open:
                            meth(r, proxy, type))

        def proxy_open(self, req, proxy, type):
            orig_type = req.type
            proxy_type, user, password, hostport = _parse_proxy(proxy)
            if proxy_type is None:
                proxy_type = orig_type

            if req.host and proxy_bypass(req.host):
                return None

            if user and password:
                user_pass = '%s:%s' % (unquote(user),
                                       unquote(password))
                creds = base64.b64encode(user_pass.encode()).decode("ascii")
                req.add_header('Proxy-authorization', 'Basic ' + creds)
            hostport = unquote(hostport)
            req.set_proxy(hostport, proxy_type)
            if orig_type == proxy_type or orig_type == 'https':
                # let other handlers take care of it
                return None
            else:
                # need to start over, because the other handlers don't
                # grok the proxy's URL type
                # e.g. if we have a constructor arg proxies like so:
                # {'http': 'ftp://proxy.example.com'}, we may end up turning
                # a request for http://acme.example.com/a into one for
                # ftp://proxy.example.com/a
                return self.parent.open(req, timeout=req.timeout)

    class HTTPPasswordMgr:

        def __init__(self):
            self.passwd = {}

        def add_password(self, realm, uri, user, passwd):
            # uri could be a single URI or a sequence
            if isinstance(uri, str):
                uri = [uri]
            if realm not in self.passwd:
                self.passwd[realm] = {}
            for default_port in True, False:
                reduced_uri = tuple(
                    self.reduce_uri(u, default_port) for u in uri)
                self.passwd[realm][reduced_uri] = (user, passwd)

        def find_user_password(self, realm, authuri):
            domains = self.passwd.get(realm, {})
            for default_port in True, False:
                reduced_authuri = self.reduce_uri(authuri, default_port)
                for uris, authinfo in domains.items():
                    for uri in uris:
                        if self.is_suburi(uri, reduced_authuri):
                            return authinfo
            return None, None

        def reduce_uri(self, uri, default_port=True):
            """Accept authority or URI and extract only the authority and path."""
            # note HTTP URLs do not have a userinfo component
            parts = urlsplit(uri)
            if parts[1]:
                # URI
                scheme = parts[0]
                authority = parts[1]
                path = parts[2] or '/'
            else:
                # host or host:port
                scheme = None
                authority = uri
                path = '/'
            host, port = _splitport(authority)
            if default_port and port is None and scheme is not None:
                dport = {"http": 80,
                         "https": 443,
                         }.get(scheme)
                if dport is not None:
                    authority = "%s:%d" % (host, dport)
            return authority, path

        def is_suburi(self, base, test):
            """Check if test is below base in a URI tree

            Both args must be URIs in reduced form.
            """
            if base == test:
                return True
            if base[0] != test[0]:
                return False
            common = posixpath.commonprefix((base[1], test[1]))
            if len(common) == len(base[1]):
                return True
            return False

    class HTTPPasswordMgrWithDefaultRealm(HTTPPasswordMgr):

        def find_user_password(self, realm, authuri):
            user, password = HTTPPasswordMgr.find_user_password(self, realm,
                                                                authuri)
            if user is not None:
                return user, password
            return HTTPPasswordMgr.find_user_password(self, None, authuri)

    class HTTPPasswordMgrWithPriorAuth(HTTPPasswordMgrWithDefaultRealm):

        def __init__(self, *args, **kwargs):
            self.authenticated = {}
            super().__init__(*args, **kwargs)

        def add_password(self, realm, uri, user, passwd, is_authenticated=False):
            self.update_authenticated(uri, is_authenticated)
            # Add a default for prior auth requests
            if realm is not None:
                super().add_password(None, uri, user, passwd)
            super().add_password(realm, uri, user, passwd)

        def update_authenticated(self, uri, is_authenticated=False):
            # uri could be a single URI or a sequence
            if isinstance(uri, str):
                uri = [uri]

            for default_port in True, False:
                for u in uri:
                    reduced_uri = self.reduce_uri(u, default_port)
                    self.authenticated[reduced_uri] = is_authenticated

        def is_authenticated(self, authuri):
            for default_port in True, False:
                reduced_authuri = self.reduce_uri(authuri, default_port)
                for uri in self.authenticated:
                    if self.is_suburi(uri, reduced_authuri):
                        return self.authenticated[uri]

    class AbstractBasicAuthHandler:

        # XXX this allows for multiple auth-schemes, but will stupidly pick
        # the last one with a realm specified.

        # allow for double- and single-quoted realm values
        # (single quotes are a violation of the RFC, but appear in the wild)
        rx = re.compile('(?:^|,)'   # start of the string or ','
                        '[ \t]*'    # optional whitespaces
                        '([^ \t]+)' # scheme like "Basic"
                        '[ \t]+'    # mandatory whitespaces
                        # realm=xxx
                        # realm='xxx'
                        # realm="xxx"
                        'realm=(["\']?)([^"\']*)\\2',
                        re.I)

        # XXX could pre-emptively send auth info already accepted (RFC 2617,
        # end of section 2, and section 1.2 immediately after "credentials"
        # production).

        def __init__(self, password_mgr=None):
            if password_mgr is None:
                password_mgr = HTTPPasswordMgr()
            self.passwd = password_mgr
            self.add_password = self.passwd.add_password

        def _parse_realm(self, header):
            # parse WWW-Authenticate header: accept multiple challenges per header
            found_challenge = False
            for mo in AbstractBasicAuthHandler.rx.finditer(header):
                scheme, quote, realm = mo.groups()
                if quote not in ['"', "'"]:
                    warnings.warn("Basic Auth Realm was unquoted",
                                  UserWarning, 3)

                yield (scheme, realm)

                found_challenge = True

            if not found_challenge:
                if header:
                    scheme = header.split()[0]
                else:
                    scheme = ''
                yield (scheme, None)

        def http_error_auth_reqed(self, authreq, host, req, headers):
            # host may be an authority (without userinfo) or a URL with an
            # authority
            headers = headers.get_all(authreq)
            if not headers:
                # no header found
                return

            unsupported = None
            for header in headers:
                for scheme, realm in self._parse_realm(header):
                    if scheme.lower() != 'basic':
                        unsupported = scheme
                        continue

                    if realm is not None:
                        # Use the first matching Basic challenge.
                        # Ignore following challenges even if they use the Basic
                        # scheme.
                        return self.retry_http_basic_auth(host, req, realm)

            if unsupported is not None:
                raise ValueError("AbstractBasicAuthHandler does not "
                                 "support the following scheme: %r"
                                 % (scheme,))

        def retry_http_basic_auth(self, host, req, realm):
            user, pw = self.passwd.find_user_password(realm, host)
            if pw is not None:
                raw = "%s:%s" % (user, pw)
                auth = "Basic " + base64.b64encode(raw.encode()).decode("ascii")
                if req.get_header(self.auth_header, None) == auth:
                    return None
                req.add_unredirected_header(self.auth_header, auth)
                return self.parent.open(req, timeout=req.timeout)
            else:
                return None

        def http_request(self, req):
            if (not hasattr(self.passwd, 'is_authenticated') or
               not self.passwd.is_authenticated(req.full_url)):
                return req

            if not req.has_header('Authorization'):
                user, passwd = self.passwd.find_user_password(None, req.full_url)
                credentials = '{0}:{1}'.format(user, passwd).encode()
                auth_str = base64.standard_b64encode(credentials).decode()
                req.add_unredirected_header('Authorization',
                                            'Basic {}'.format(auth_str.strip()))
            return req

        def http_response(self, req, response):
            if hasattr(self.passwd, 'is_authenticated'):
                if 200 <= response.code < 300:
                    self.passwd.update_authenticated(req.full_url, True)
                else:
                    self.passwd.update_authenticated(req.full_url, False)
            return response

        https_request = http_request
        https_response = http_response

    class HTTPBasicAuthHandler(AbstractBasicAuthHandler, BaseHandler):

        auth_header = 'Authorization'

        def http_error_401(self, req, fp, code, msg, headers):
            url = req.full_url
            response = self.http_error_auth_reqed('www-authenticate',
                                              url, req, headers)
            return response

    class ProxyBasicAuthHandler(AbstractBasicAuthHandler, BaseHandler):

        auth_header = 'Proxy-authorization'

        def http_error_407(self, req, fp, code, msg, headers):
            # http_error_auth_reqed requires that there is no userinfo component in
            # authority.  Assume there isn't one, since urllib.request does not (and
            # should not, RFC 3986 s. 3.2.1) support requests for URLs containing
            # userinfo.
            authority = req.host
            response = self.http_error_auth_reqed('proxy-authenticate',
                                              authority, req, headers)
            return response

    # Return n random bytes.
    _randombytes = os.urandom

    class AbstractDigestAuthHandler:
        # Digest authentication is specified in RFC 2617.

        # XXX The client does not inspect the Authentication-Info header
        # in a successful response.

        # XXX It should be possible to test this implementation against
        # a mock server that just generates a static set of challenges.

        # XXX qop="auth-int" supports is shaky

        def __init__(self, passwd=None):
            if passwd is None:
                passwd = HTTPPasswordMgr()
            self.passwd = passwd
            self.add_password = self.passwd.add_password
            self.retried = 0
            self.nonce_count = 0
            self.last_nonce = None

        def reset_retry_count(self):
            self.retried = 0

        def http_error_auth_reqed(self, auth_header, host, req, headers):
            authreq = headers.get(auth_header, None)
            if self.retried > 5:
                # Don't fail endlessly - if we failed once, we'll probably
                # fail a second time. Hm. Unless the Password Manager is
                # prompting for the information. Crap. This isn't great
                # but it's better than the current 'repeat until recursion
                # depth exceeded' approach <wink>
                raise HTTPError(req.full_url, 401, "digest auth failed",
                                headers, None)
            else:
                self.retried += 1
            if authreq:
                scheme = authreq.split()[0]
                if scheme.lower() == 'digest':
                    return self.retry_http_digest_auth(req, authreq)
                elif scheme.lower() != 'basic':
                    raise ValueError("AbstractDigestAuthHandler does not support"
                                     " the following scheme: '%s'" % scheme)

        def retry_http_digest_auth(self, req, auth):
            token, challenge = auth.split(' ', 1)
            chal = parse_keqv_list(filter(None, parse_http_list(challenge)))
            auth = self.get_authorization(req, chal)
            if auth:
                auth_val = 'Digest %s' % auth
                if req.headers.get(self.auth_header, None) == auth_val:
                    return None
                req.add_unredirected_header(self.auth_header, auth_val)
                resp = self.parent.open(req, timeout=req.timeout)
                return resp

        def get_cnonce(self, nonce):
            # The cnonce-value is an opaque
            # quoted string value provided by the client and used by both client
            # and server to avoid chosen plaintext attacks, to provide mutual
            # authentication, and to provide some message integrity protection.
            # This isn't a fabulous effort, but it's probably Good Enough.
            s = "%s:%s:%s:" % (self.nonce_count, nonce, time.ctime())
            b = s.encode("ascii") + _randombytes(8)
            dig = hashlib.sha1(b).hexdigest()
            return dig[:16]

        def get_authorization(self, req, chal):
            try:
                realm = chal['realm']
                nonce = chal['nonce']
                qop = chal.get('qop')
                algorithm = chal.get('algorithm', 'MD5')
                # mod_digest doesn't send an opaque, even though it isn't
                # supposed to be optional
                opaque = chal.get('opaque', None)
            except KeyError:
                return None

            H, KD = self.get_algorithm_impls(algorithm)
            if H is None:
                return None

            user, pw = self.passwd.find_user_password(realm, req.full_url)
            if user is None:
                return None

            # XXX not implemented yet
            if req.data is not None:
                entdig = self.get_entity_digest(req.data, chal)
            else:
                entdig = None

            A1 = "%s:%s:%s" % (user, realm, pw)
            A2 = "%s:%s" % (req.get_method(),
                            # XXX selector: what about proxies and full urls
                            req.selector)
            # NOTE: As per  RFC 2617, when server sends "auth,auth-int", the client could use either `auth`
            #     or `auth-int` to the response back. we use `auth` to send the response back.
            if qop is None:
                respdig = KD(H(A1), "%s:%s" % (nonce, H(A2)))
            elif 'auth' in qop.split(','):
                if nonce == self.last_nonce:
                    self.nonce_count += 1
                else:
                    self.nonce_count = 1
                    self.last_nonce = nonce
                ncvalue = '%08x' % self.nonce_count
                cnonce = self.get_cnonce(nonce)
                noncebit = "%s:%s:%s:%s:%s" % (nonce, ncvalue, cnonce, 'auth', H(A2))
                respdig = KD(H(A1), noncebit)
            else:
                # XXX handle auth-int.
                raise URLError("qop '%s' is not supported." % qop)

            # XXX should the partial digests be encoded too?

            base = 'username="%s", realm="%s", nonce="%s", uri="%s", ' \
                   'response="%s"' % (user, realm, nonce, req.selector,
                                      respdig)
            if opaque:
                base += ', opaque="%s"' % opaque
            if entdig:
                base += ', digest="%s"' % entdig
            base += ', algorithm="%s"' % algorithm
            if qop:
                base += ', qop=auth, nc=%s, cnonce="%s"' % (ncvalue, cnonce)
            return base

        def get_algorithm_impls(self, algorithm):
            # lambdas assume digest modules are imported at the top level
            if algorithm == 'MD5':
                H = lambda x: hashlib.md5(x.encode("ascii")).hexdigest()
            elif algorithm == 'SHA':
                H = lambda x: hashlib.sha1(x.encode("ascii")).hexdigest()
            # XXX MD5-sess
            else:
                raise ValueError("Unsupported digest authentication "
                                 "algorithm %r" % algorithm)
            KD = lambda s, d: H("%s:%s" % (s, d))
            return H, KD

        def get_entity_digest(self, data, chal):
            # XXX not implemented yet
            return None

    class HTTPDigestAuthHandler(BaseHandler, AbstractDigestAuthHandler):
        """An authentication protocol defined by RFC 2069

        Digest authentication improves on basic authentication because it
        does not transmit passwords in the clear.
        """

        auth_header = 'Authorization'
        handler_order = 490  # before Basic auth

        def http_error_401(self, req, fp, code, msg, headers):
            host = urlparse(req.full_url)[1]
            retry = self.http_error_auth_reqed('www-authenticate',
                                               host, req, headers)
            self.reset_retry_count()
            return retry

    class ProxyDigestAuthHandler(BaseHandler, AbstractDigestAuthHandler):

        auth_header = 'Proxy-Authorization'
        handler_order = 490  # before Basic auth

        def http_error_407(self, req, fp, code, msg, headers):
            host = req.host
            retry = self.http_error_auth_reqed('proxy-authenticate',
                                               host, req, headers)
            self.reset_retry_count()
            return retry

    class AbstractHTTPHandler(BaseHandler):

        def __init__(self, debuglevel=0):
            self._debuglevel = debuglevel

        def set_http_debuglevel(self, level):
            self._debuglevel = level

        def _get_content_length(self, request):
            return http.client.HTTPConnection._get_content_length(
                request.data,
                request.get_method())

        def do_request_(self, request):
            host = request.host
            if not host:
                raise URLError('no host given')

            if request.data is not None:  # POST
                data = request.data
                if isinstance(data, str):
                    msg = "POST data should be bytes, an iterable of bytes, " \
                          "or a file object. It cannot be of type str."
                    raise TypeError(msg)
                if not request.has_header('Content-type'):
                    request.add_unredirected_header(
                        'Content-type',
                        'application/x-www-form-urlencoded')
                if (not request.has_header('Content-length')
                        and not request.has_header('Transfer-encoding')):
                    content_length = self._get_content_length(request)
                    if content_length is not None:
                        request.add_unredirected_header(
                                'Content-length', str(content_length))
                    else:
                        request.add_unredirected_header(
                                'Transfer-encoding', 'chunked')

            sel_host = host
            if request.has_proxy():
                scheme, sel = _splittype(request.selector)
                sel_host, sel_path = _splithost(sel)
            if not request.has_header('Host'):
                request.add_unredirected_header('Host', sel_host)
            for name, value in self.parent.addheaders:
                name = name.capitalize()
                if not request.has_header(name):
                    request.add_unredirected_header(name, value)

            return request

        def do_open(self, http_class, req, **http_conn_args):
            """Return an HTTPResponse object for the request, using http_class.

            http_class must implement the HTTPConnection API from http.client.
            """
            host = req.host
            if not host:
                raise URLError('no host given')

            # will parse host:port
            h = http_class(host, timeout=req.timeout, **http_conn_args)
            h.set_debuglevel(self._debuglevel)

            headers = dict(req.unredirected_hdrs)
            headers.update({k: v for k, v in req.headers.items()
                            if k not in headers})

            # TODO(jhylton): Should this be redesigned to handle
            # persistent connections?

            # We want to make an HTTP/1.1 request, but the addinfourl
            # class isn't prepared to deal with a persistent connection.
            # It will try to read all remaining data from the socket,
            # which will block while the server waits for the next request.
            # So make sure the connection gets closed after the (only)
            # request.
            headers["Connection"] = "close"
            headers = {name.title(): val for name, val in headers.items()}

            if req._tunnel_host:
                tunnel_headers = {}
                proxy_auth_hdr = "Proxy-Authorization"
                if proxy_auth_hdr in headers:
                    tunnel_headers[proxy_auth_hdr] = headers[proxy_auth_hdr]
                    # Proxy-Authorization should not be sent to origin
                    # server.
                    del headers[proxy_auth_hdr]
                h.set_tunnel(req._tunnel_host, headers=tunnel_headers)

            try:
                try:
                    h.request(req.get_method(), req.selector, req.data, headers,
                              encode_chunked=req.has_header('Transfer-encoding'))
                except OSError as err: # timeout error
                    raise URLError(err)
                r = h.getresponse()
            except:
                h.close()
                raise

            # If the server does not send us a 'Connection: close' header,
            # HTTPConnection assumes the socket should be left open. Manually
            # mark the socket to be closed when this response object goes away.
            if h.sock:
                h.sock.close()
                h.sock = None

            r.url = req.get_full_url()
            # This line replaces the .msg attribute of the HTTPResponse
            # with .headers, because urllib clients expect the response to
            # have the reason in .msg.  It would be good to mark this
            # attribute is deprecated and get then to use info() or
            # .headers.
            r.msg = r.reason
            return r

    class HTTPHandler(AbstractHTTPHandler):

        def http_open(self, req):
            return self.do_open(http.client.HTTPConnection, req)

        http_request = AbstractHTTPHandler.do_request_

    if hasattr(http.client, 'HTTPSConnection'):

        class HTTPSHandler(AbstractHTTPHandler):

            def __init__(self, debuglevel=0, context=None, check_hostname=None):
                AbstractHTTPHandler.__init__(self, debuglevel)
                self._context = context
                self._check_hostname = check_hostname

            def https_open(self, req):
                return self.do_open(http.client.HTTPSConnection, req,
                    context=self._context, check_hostname=self._check_hostname)

            https_request = AbstractHTTPHandler.do_request_

        __all__.append('HTTPSHandler')

    class HTTPCookieProcessor(BaseHandler):
        def __init__(self, cookiejar=None):
            import http.cookiejar
            if cookiejar is None:
                cookiejar = http.cookiejar.CookieJar()
            self.cookiejar = cookiejar

        def http_request(self, request):
            self.cookiejar.add_cookie_header(request)
            return request

        def http_response(self, request, response):
            self.cookiejar.extract_cookies(response, request)
            return response

        https_request = http_request
        https_response = http_response

    class UnknownHandler(BaseHandler):
        def unknown_open(self, req):
            type = req.type
            raise URLError('unknown url type: %s' % type)

    def parse_keqv_list(l):
        """Parse list of key=value strings where keys are not duplicated."""
        parsed = {}
        for elt in l:
            k, v = elt.split('=', 1)
            if v[0] == '"' and v[-1] == '"':
                v = v[1:-1]
            parsed[k] = v
        return parsed

    def parse_http_list(s):
        """Parse lists as described by RFC 2068 Section 2.

        In particular, parse comma-separated lists where the elements of
        the list may include quoted-strings.  A quoted-string could
        contain a comma.  A non-quoted string could have quotes in the
        middle.  Neither commas nor quotes count if they are escaped.
        Only double-quotes count, not single-quotes.
        """
        res = []
        part = ''

        escape = quote = False
        for cur in s:
            if escape:
                part += cur
                escape = False
                continue
            if quote:
                if cur == '\\':
                    escape = True
                    continue
                elif cur == '"':
                    quote = False
                part += cur
                continue

            if cur == ',':
                res.append(part)
                part = ''
                continue

            if cur == '"':
                quote = True

            part += cur

        # append last part
        if part:
            res.append(part)

        return [part.strip() for part in res]

    class FileHandler(BaseHandler):
        # Use local file or FTP depending on form of URL
        def file_open(self, req):
            url = req.selector
            if url[:2] == '//' and url[2:3] != '/' and (req.host and
                    req.host != 'localhost'):
                if not req.host in self.get_names():
                    raise URLError("file:// scheme is supported only on localhost")
            else:
                return self.open_local_file(req)

        # names for the localhost
        names = None
        def get_names(self):
            if FileHandler.names is None:
                try:
                    FileHandler.names = tuple(
                        socket.gethostbyname_ex('localhost')[2] +
                        socket.gethostbyname_ex(socket.gethostname())[2])
                except socket.gaierror:
                    FileHandler.names = (socket.gethostbyname('localhost'),)
            return FileHandler.names

        # not entirely sure what the rules are here
        def open_local_file(self, req):
            import email.utils
            import mimetypes
            host = req.host
            filename = req.selector
            localfile = url2pathname(filename)
            try:
                stats = os.stat(localfile)
                size = stats.st_size
                modified = email.utils.formatdate(stats.st_mtime, usegmt=True)
                mtype = mimetypes.guess_type(filename)[0]
                headers = email.message_from_string(
                    'Content-type: %s\nContent-length: %d\nLast-modified: %s\n' %
                    (mtype or 'text/plain', size, modified))
                if host:
                    host, port = _splitport(host)
                if not host or \
                    (not port and _safe_gethostbyname(host) in self.get_names()):
                    if host:
                        origurl = 'file://' + host + filename
                    else:
                        origurl = 'file://' + filename
                    return addinfourl(open(localfile, 'rb'), headers, origurl)
            except OSError as exp:
                raise URLError(exp)
            raise URLError('file not on local host')

    def _safe_gethostbyname(host):
        try:
            return socket.gethostbyname(host)
        except socket.gaierror:
            return None

    class FTPHandler(BaseHandler):
        def ftp_open(self, req):
            import ftplib
            import mimetypes
            host = req.host
            if not host:
                raise URLError('ftp error: no host given')
            host, port = _splitport(host)
            if port is None:
                port = ftplib.FTP_PORT
            else:
                port = int(port)

            # username/password handling
            user, host = _splituser(host)
            if user:
                user, passwd = _splitpasswd(user)
            else:
                passwd = None
            host = unquote(host)
            user = user or ''
            passwd = passwd or ''

            try:
                host = socket.gethostbyname(host)
            except OSError as msg:
                raise URLError(msg)
            path, attrs = _splitattr(req.selector)
            dirs = path.split('/')
            dirs = list(map(unquote, dirs))
            dirs, file = dirs[:-1], dirs[-1]
            if dirs and not dirs[0]:
                dirs = dirs[1:]
            try:
                fw = self.connect_ftp(user, passwd, host, port, dirs, req.timeout)
                type = file and 'I' or 'D'
                for attr in attrs:
                    attr, value = _splitvalue(attr)
                    if attr.lower() == 'type' and \
                       value in ('a', 'A', 'i', 'I', 'd', 'D'):
                        type = value.upper()
                fp, retrlen = fw.retrfile(file, type)
                headers = ""
                mtype = mimetypes.guess_type(req.full_url)[0]
                if mtype:
                    headers += "Content-type: %s\n" % mtype
                if retrlen is not None and retrlen >= 0:
                    headers += "Content-length: %d\n" % retrlen
                headers = email.message_from_string(headers)
                return addinfourl(fp, headers, req.full_url)
            except ftplib.all_errors as exp:
                exc = URLError('ftp error: %r' % exp)
                raise exc.with_traceback(sys.exc_info()[2])

        def connect_ftp(self, user, passwd, host, port, dirs, timeout):
            return ftpwrapper(user, passwd, host, port, dirs, timeout,
                              persistent=False)

    class CacheFTPHandler(FTPHandler):
        # XXX would be nice to have pluggable cache strategies
        # XXX this stuff is definitely not thread safe
        def __init__(self):
            self.cache = {}
            self.timeout = {}
            self.soonest = 0
            self.delay = 60
            self.max_conns = 16

        def setTimeout(self, t):
            self.delay = t

        def setMaxConns(self, m):
            self.max_conns = m

        def connect_ftp(self, user, passwd, host, port, dirs, timeout):
            key = user, host, port, '/'.join(dirs), timeout
            if key in self.cache:
                self.timeout[key] = time.time() + self.delay
            else:
                self.cache[key] = ftpwrapper(user, passwd, host, port,
                                             dirs, timeout)
                self.timeout[key] = time.time() + self.delay
            self.check_cache()
            return self.cache[key]

        def check_cache(self):
            # first check for old ones
            t = time.time()
            if self.soonest <= t:
                for k, v in list(self.timeout.items()):
                    if v < t:
                        self.cache[k].close()
                        del self.cache[k]
                        del self.timeout[k]
            self.soonest = min(list(self.timeout.values()))

            # then check the size
            if len(self.cache) == self.max_conns:
                for k, v in list(self.timeout.items()):
                    if v == self.soonest:
                        del self.cache[k]
                        del self.timeout[k]
                        break
                self.soonest = min(list(self.timeout.values()))

        def clear_cache(self):
            for conn in self.cache.values():
                conn.close()
            self.cache.clear()
            self.timeout.clear()

    class DataHandler(BaseHandler):
        def data_open(self, req):
            # data URLs as specified in RFC 2397.
            #
            # ignores POSTed data
            #
            # syntax:
            # dataurl   := "data:" [ mediatype ] [ ";base64" ] "," data
            # mediatype := [ type "/" subtype ] *( ";" parameter )
            # data      := *urlchar
            # parameter := attribute "=" value
            url = req.full_url

            scheme, data = url.split(":",1)
            mediatype, data = data.split(",",1)

            # even base64 encoded data URLs might be quoted so unquote in any case:
            data = unquote_to_bytes(data)
            if mediatype.endswith(";base64"):
                data = base64.decodebytes(data)
                mediatype = mediatype[:-7]

            if not mediatype:
                mediatype = "text/plain;charset=US-ASCII"

            headers = email.message_from_string("Content-type: %s\nContent-length: %d\n" %
                (mediatype, len(data)))

            return addinfourl(io.BytesIO(data), headers, url)

    # Code move from the old urllib module

    MAXFTPCACHE = 10        # Trim the ftp cache beyond this size

    # Helper for non-unix systems
    if os.name == 'nt':
        from nturl2path import url2pathname, pathname2url
    else:
        def url2pathname(pathname):
            """OS-specific conversion from a relative URL of the 'file' scheme
            to a file system path; not recommended for general use."""
            return unquote(pathname)

        def pathname2url(pathname):
            """OS-specific conversion from a file system path to a relative URL
            of the 'file' scheme; not recommended for general use."""
            return quote(pathname)

    ftpcache = {}

    class URLopener:
        """Class to open URLs.
        This is a class rather than just a subroutine because we may need
        more than one set of global protocol-specific options.
        Note -- this is a base class for those who don't want the
        automatic handling of errors type 302 (relocated) and 401
        (authorization needed)."""

        __tempfiles = None

        version = "Python-urllib/%s" % __version__

        # Constructor
        def __init__(self, proxies=None, **x509):
            msg = "%(class)s style of invoking requests is deprecated. " \
                  "Use newer urlopen functions/methods" % {'class': self.__class__.__name__}
            warnings.warn(msg, DeprecationWarning, stacklevel=3)
            if proxies is None:
                proxies = getproxies()
            assert hasattr(proxies, 'keys'), "proxies must be a mapping"
            self.proxies = proxies
            self.key_file = x509.get('key_file')
            self.cert_file = x509.get('cert_file')
            self.addheaders = [('User-Agent', self.version), ('Accept', '*/*')]
            self.__tempfiles = []
            self.__unlink = os.unlink # See cleanup()
            self.tempcache = None
            # Undocumented feature: if you assign {} to tempcache,
            # it is used to cache files retrieved with
            # self.retrieve().  This is not enabled by default
            # since it does not work for changing documents (and I
            # haven't got the logic to check expiration headers
            # yet).
            self.ftpcache = ftpcache
            # Undocumented feature: you can use a different
            # ftp cache by assigning to the .ftpcache member;
            # in case you want logically independent URL openers
            # XXX This is not threadsafe.  Bah.

        def __del__(self):
            self.close()

        def close(self):
            self.cleanup()

        def cleanup(self):
            # This code sometimes runs when the rest of this module
            # has already been deleted, so it can't use any globals
            # or import anything.
            if self.__tempfiles:
                for file in self.__tempfiles:
                    try:
                        self.__unlink(file)
                    except OSError:
                        pass
                del self.__tempfiles[:]
            if self.tempcache:
                self.tempcache.clear()

        def addheader(self, *args):
            """Add a header to be used by the HTTP interface only
            e.g. u.addheader('Accept', 'sound/basic')"""
            self.addheaders.append(args)

        # External interface
        def open(self, fullurl, data=None):
            """Use URLopener().open(file) instead of open(file, 'r')."""
            fullurl = unwrap(_to_bytes(fullurl))
            fullurl = quote(fullurl, safe="%/:=&?~#+!$,;'@()*[]|")
            if self.tempcache and fullurl in self.tempcache:
                filename, headers = self.tempcache[fullurl]
                fp = open(filename, 'rb')
                return addinfourl(fp, headers, fullurl)
            urltype, url = _splittype(fullurl)
            if not urltype:
                urltype = 'file'
            if urltype in self.proxies:
                proxy = self.proxies[urltype]
                urltype, proxyhost = _splittype(proxy)
                host, selector = _splithost(proxyhost)
                url = (host, fullurl) # Signal special case to open_*()
            else:
                proxy = None
            name = 'open_' + urltype
            self.type = urltype
            name = name.replace('-', '_')
            if not hasattr(self, name) or name == 'open_local_file':
                if proxy:
                    return self.open_unknown_proxy(proxy, fullurl, data)
                else:
                    return self.open_unknown(fullurl, data)
            try:
                if data is None:
                    return getattr(self, name)(url)
                else:
                    return getattr(self, name)(url, data)
            except (HTTPError, URLError):
                raise
            except OSError as msg:
                raise OSError('socket error', msg).with_traceback(sys.exc_info()[2])

        def open_unknown(self, fullurl, data=None):
            """Overridable interface to open unknown URL type."""
            type, url = _splittype(fullurl)
            raise OSError('url error', 'unknown url type', type)

        def open_unknown_proxy(self, proxy, fullurl, data=None):
            """Overridable interface to open unknown URL type."""
            type, url = _splittype(fullurl)
            raise OSError('url error', 'invalid proxy for %s' % type, proxy)

        # External interface
        def retrieve(self, url, filename=None, reporthook=None, data=None):
            """retrieve(url) returns (filename, headers) for a local object
            or (tempfilename, headers) for a remote object."""
            url = unwrap(_to_bytes(url))
            if self.tempcache and url in self.tempcache:
                return self.tempcache[url]
            type, url1 = _splittype(url)
            if filename is None and (not type or type == 'file'):
                try:
                    fp = self.open_local_file(url1)
                    hdrs = fp.info()
                    fp.close()
                    return url2pathname(_splithost(url1)[1]), hdrs
                except OSError as msg:
                    pass
            fp = self.open(url, data)
            try:
                headers = fp.info()
                if filename:
                    tfp = open(filename, 'wb')
                else:
                    garbage, path = _splittype(url)
                    garbage, path = _splithost(path or "")
                    path, garbage = _splitquery(path or "")
                    path, garbage = _splitattr(path or "")
                    suffix = os.path.splitext(path)[1]
                    (fd, filename) = tempfile.mkstemp(suffix)
                    self.__tempfiles.append(filename)
                    tfp = os.fdopen(fd, 'wb')
                try:
                    result = filename, headers
                    if self.tempcache is not None:
                        self.tempcache[url] = result
                    bs = 1024*8
                    size = -1
                    read = 0
                    blocknum = 0
                    if "content-length" in headers:
                        size = int(headers["Content-Length"])
                    if reporthook:
                        reporthook(blocknum, bs, size)
                    while 1:
                        block = fp.read(bs)
                        if not block:
                            break
                        read += len(block)
                        tfp.write(block)
                        blocknum += 1
                        if reporthook:
                            reporthook(blocknum, bs, size)
                finally:
                    tfp.close()
            finally:
                fp.close()

            # raise exception if actual size does not match content-length header
            if size >= 0 and read < size:
                raise ContentTooShortError(
                    "retrieval incomplete: got only %i out of %i bytes"
                    % (read, size), result)

            return result

        # Each method named open_<type> knows how to open that type of URL

        def _open_generic_http(self, connection_factory, url, data):
            """Make an HTTP connection using connection_class.

            This is an internal method that should be called from
            open_http() or open_https().

            Arguments:
            - connection_factory should take a host name and return an
              HTTPConnection instance.
            - url is the url to retrieval or a host, relative-path pair.
            - data is payload for a POST request or None.
            """

            user_passwd = None
            proxy_passwd= None
            if isinstance(url, str):
                host, selector = _splithost(url)
                if host:
                    user_passwd, host = _splituser(host)
                    host = unquote(host)
                realhost = host
            else:
                host, selector = url
                # check whether the proxy contains authorization information
                proxy_passwd, host = _splituser(host)
                # now we proceed with the url we want to obtain
                urltype, rest = _splittype(selector)
                url = rest
                user_passwd = None
                if urltype.lower() != 'http':
                    realhost = None
                else:
                    realhost, rest = _splithost(rest)
                    if realhost:
                        user_passwd, realhost = _splituser(realhost)
                    if user_passwd:
                        selector = "%s://%s%s" % (urltype, realhost, rest)
                    if proxy_bypass(realhost):
                        host = realhost

            if not host: raise OSError('http error', 'no host given')

            if proxy_passwd:
                proxy_passwd = unquote(proxy_passwd)
                proxy_auth = base64.b64encode(proxy_passwd.encode()).decode('ascii')
            else:
                proxy_auth = None

            if user_passwd:
                user_passwd = unquote(user_passwd)
                auth = base64.b64encode(user_passwd.encode()).decode('ascii')
            else:
                auth = None
            http_conn = connection_factory(host)
            headers = {}
            if proxy_auth:
                headers["Proxy-Authorization"] = "Basic %s" % proxy_auth
            if auth:
                headers["Authorization"] =  "Basic %s" % auth
            if realhost:
                headers["Host"] = realhost

            # Add Connection:close as we don't support persistent connections yet.
            # This helps in closing the socket and avoiding ResourceWarning

            headers["Connection"] = "close"

            for header, value in self.addheaders:
                headers[header] = value

            if data is not None:
                headers["Content-Type"] = "application/x-www-form-urlencoded"
                http_conn.request("POST", selector, data, headers)
            else:
                http_conn.request("GET", selector, headers=headers)

            try:
                response = http_conn.getresponse()
            except http.client.BadStatusLine:
                # something went wrong with the HTTP status line
                raise URLError("http protocol error: bad status line")

            # According to RFC 2616, "2xx" code indicates that the client's
            # request was successfully received, understood, and accepted.
            if 200 <= response.status < 300:
                return addinfourl(response, response.msg, "http:" + url,
                                  response.status)
            else:
                return self.http_error(
                    url, response.fp,
                    response.status, response.reason, response.msg, data)

        def open_http(self, url, data=None):
            """Use HTTP protocol."""
            return self._open_generic_http(http.client.HTTPConnection, url, data)

        def http_error(self, url, fp, errcode, errmsg, headers, data=None):
            """Handle http errors.

            Derived class can override this, or provide specific handlers
            named http_error_DDD where DDD is the 3-digit error code."""
            # First check if there's a specific handler for this error
            name = 'http_error_%d' % errcode
            if hasattr(self, name):
                method = getattr(self, name)
                if data is None:
                    result = method(url, fp, errcode, errmsg, headers)
                else:
                    result = method(url, fp, errcode, errmsg, headers, data)
                if result: return result
            return self.http_error_default(url, fp, errcode, errmsg, headers)

        def http_error_default(self, url, fp, errcode, errmsg, headers):
            """Default error handler: close the connection and raise OSError."""
            fp.close()
            raise HTTPError(url, errcode, errmsg, headers, None)

        if _have_ssl:
            def _https_connection(self, host):
                return http.client.HTTPSConnection(host,
                                               key_file=self.key_file,
                                               cert_file=self.cert_file)

            def open_https(self, url, data=None):
                """Use HTTPS protocol."""
                return self._open_generic_http(self._https_connection, url, data)

        def open_file(self, url):
            """Use local file or FTP depending on form of URL."""
            if not isinstance(url, str):
                raise URLError('file error: proxy support for file protocol currently not implemented')
            if url[:2] == '//' and url[2:3] != '/' and url[2:12].lower() != 'localhost/':
                raise ValueError("file:// scheme is supported only on localhost")
            else:
                return self.open_local_file(url)

        def open_local_file(self, url):
            """Use local file."""
            import email.utils
            import mimetypes
            host, file = _splithost(url)
            localname = url2pathname(file)
            try:
                stats = os.stat(localname)
            except OSError as e:
                raise URLError(e.strerror, e.filename)
            size = stats.st_size
            modified = email.utils.formatdate(stats.st_mtime, usegmt=True)
            mtype = mimetypes.guess_type(url)[0]
            headers = email.message_from_string(
                'Content-Type: %s\nContent-Length: %d\nLast-modified: %s\n' %
                (mtype or 'text/plain', size, modified))
            if not host:
                urlfile = file
                if file[:1] == '/':
                    urlfile = 'file://' + file
                return addinfourl(open(localname, 'rb'), headers, urlfile)
            host, port = _splitport(host)
            if (not port
               and socket.gethostbyname(host) in ((localhost(),) + thishost())):
                urlfile = file
                if file[:1] == '/':
                    urlfile = 'file://' + file
                elif file[:2] == './':
                    raise ValueError("local file url may start with / or file:. Unknown url of type: %s" % url)
                return addinfourl(open(localname, 'rb'), headers, urlfile)
            raise URLError('local file error: not on local host')

        def open_ftp(self, url):
            """Use FTP protocol."""
            if not isinstance(url, str):
                raise URLError('ftp error: proxy support for ftp protocol currently not implemented')
            import mimetypes
            host, path = _splithost(url)
            if not host: raise URLError('ftp error: no host given')
            host, port = _splitport(host)
            user, host = _splituser(host)
            if user: user, passwd = _splitpasswd(user)
            else: passwd = None
            host = unquote(host)
            user = unquote(user or '')
            passwd = unquote(passwd or '')
            host = socket.gethostbyname(host)
            if not port:
                import ftplib
                port = ftplib.FTP_PORT
            else:
                port = int(port)
            path, attrs = _splitattr(path)
            path = unquote(path)
            dirs = path.split('/')
            dirs, file = dirs[:-1], dirs[-1]
            if dirs and not dirs[0]: dirs = dirs[1:]
            if dirs and not dirs[0]: dirs[0] = '/'
            key = user, host, port, '/'.join(dirs)
            # XXX thread unsafe!
            if len(self.ftpcache) > MAXFTPCACHE:
                # Prune the cache, rather arbitrarily
                for k in list(self.ftpcache):
                    if k != key:
                        v = self.ftpcache[k]
                        del self.ftpcache[k]
                        v.close()
            try:
                if key not in self.ftpcache:
                    self.ftpcache[key] = \
                        ftpwrapper(user, passwd, host, port, dirs)
                if not file: type = 'D'
                else: type = 'I'
                for attr in attrs:
                    attr, value = _splitvalue(attr)
                    if attr.lower() == 'type' and \
                       value in ('a', 'A', 'i', 'I', 'd', 'D'):
                        type = value.upper()
                (fp, retrlen) = self.ftpcache[key].retrfile(file, type)
                mtype = mimetypes.guess_type("ftp:" + url)[0]
                headers = ""
                if mtype:
                    headers += "Content-Type: %s\n" % mtype
                if retrlen is not None and retrlen >= 0:
                    headers += "Content-Length: %d\n" % retrlen
                headers = email.message_from_string(headers)
                return addinfourl(fp, headers, "ftp:" + url)
            except ftperrors() as exp:
                raise URLError('ftp error %r' % exp).with_traceback(sys.exc_info()[2])

        def open_data(self, url, data=None):
            """Use "data" URL."""
            if not isinstance(url, str):
                raise URLError('data error: proxy support for data protocol currently not implemented')
            # ignore POSTed data
            #
            # syntax of data URLs:
            # dataurl   := "data:" [ mediatype ] [ ";base64" ] "," data
            # mediatype := [ type "/" subtype ] *( ";" parameter )
            # data      := *urlchar
            # parameter := attribute "=" value
            try:
                [type, data] = url.split(',', 1)
            except ValueError:
                raise OSError('data error', 'bad data URL')
            if not type:
                type = 'text/plain;charset=US-ASCII'
            semi = type.rfind(';')
            if semi >= 0 and '=' not in type[semi:]:
                encoding = type[semi+1:]
                type = type[:semi]
            else:
                encoding = ''
            msg = []
            msg.append('Date: %s'%time.strftime('%a, %d %b %Y %H:%M:%S GMT',
                                                time.gmtime(time.time())))
            msg.append('Content-type: %s' % type)
            if encoding == 'base64':
                # XXX is this encoding/decoding ok?
                data = base64.decodebytes(data.encode('ascii')).decode('latin-1')
            else:
                data = unquote(data)
            msg.append('Content-Length: %d' % len(data))
            msg.append('')
            msg.append(data)
            msg = '\n'.join(msg)
            headers = email.message_from_string(msg)
            f = io.StringIO(msg)
            #f.fileno = None     # needed for addinfourl
            return addinfourl(f, headers, url)

    class FancyURLopener(URLopener):
        """Derived class with handlers for errors we can handle (perhaps)."""

        def __init__(self, *args, **kwargs):
            URLopener.__init__(self, *args, **kwargs)
            self.auth_cache = {}
            self.tries = 0
            self.maxtries = 10

        def http_error_default(self, url, fp, errcode, errmsg, headers):
            """Default error handling -- don't raise an exception."""
            return addinfourl(fp, headers, "http:" + url, errcode)

        def http_error_302(self, url, fp, errcode, errmsg, headers, data=None):
            """Error 302 -- relocated (temporarily)."""
            self.tries += 1
            try:
                if self.maxtries and self.tries >= self.maxtries:
                    if hasattr(self, "http_error_500"):
                        meth = self.http_error_500
                    else:
                        meth = self.http_error_default
                    return meth(url, fp, 500,
                                "Internal Server Error: Redirect Recursion",
                                headers)
                result = self.redirect_internal(url, fp, errcode, errmsg,
                                                headers, data)
                return result
            finally:
                self.tries = 0

        def redirect_internal(self, url, fp, errcode, errmsg, headers, data):
            if 'location' in headers:
                newurl = headers['location']
            elif 'uri' in headers:
                newurl = headers['uri']
            else:
                return
            fp.close()

            # In case the server sent a relative URL, join with original:
            newurl = urljoin(self.type + ":" + url, newurl)

            urlparts = urlparse(newurl)

            # For security reasons, we don't allow redirection to anything other
            # than http, https and ftp.

            # We are using newer HTTPError with older redirect_internal method
            # This older method will get deprecated in 3.3

            if urlparts.scheme not in ('http', 'https', 'ftp', ''):
                raise HTTPError(newurl, errcode,
                                errmsg +
                                " Redirection to url '%s' is not allowed." % newurl,
                                headers, fp)

            return self.open(newurl)

        def http_error_301(self, url, fp, errcode, errmsg, headers, data=None):
            """Error 301 -- also relocated (permanently)."""
            return self.http_error_302(url, fp, errcode, errmsg, headers, data)

        def http_error_303(self, url, fp, errcode, errmsg, headers, data=None):
            """Error 303 -- also relocated (essentially identical to 302)."""
            return self.http_error_302(url, fp, errcode, errmsg, headers, data)

        def http_error_307(self, url, fp, errcode, errmsg, headers, data=None):
            """Error 307 -- relocated, but turn POST into error."""
            if data is None:
                return self.http_error_302(url, fp, errcode, errmsg, headers, data)
            else:
                return self.http_error_default(url, fp, errcode, errmsg, headers)

        def http_error_401(self, url, fp, errcode, errmsg, headers, data=None,
                retry=False):
            """Error 401 -- authentication required.
            This function supports Basic authentication only."""
            if 'www-authenticate' not in headers:
                URLopener.http_error_default(self, url, fp,
                                             errcode, errmsg, headers)
            stuff = headers['www-authenticate']
            match = re.match('[ \t]*([^ \t]+)[ \t]+realm="([^"]*)"', stuff)
            if not match:
                URLopener.http_error_default(self, url, fp,
                                             errcode, errmsg, headers)
            scheme, realm = match.groups()
            if scheme.lower() != 'basic':
                URLopener.http_error_default(self, url, fp,
                                             errcode, errmsg, headers)
            if not retry:
                URLopener.http_error_default(self, url, fp, errcode, errmsg,
                        headers)
            name = 'retry_' + self.type + '_basic_auth'
            if data is None:
                return getattr(self,name)(url, realm)
            else:
                return getattr(self,name)(url, realm, data)

        def http_error_407(self, url, fp, errcode, errmsg, headers, data=None,
                retry=False):
            """Error 407 -- proxy authentication required.
            This function supports Basic authentication only."""
            if 'proxy-authenticate' not in headers:
                URLopener.http_error_default(self, url, fp,
                                             errcode, errmsg, headers)
            stuff = headers['proxy-authenticate']
            match = re.match('[ \t]*([^ \t]+)[ \t]+realm="([^"]*)"', stuff)
            if not match:
                URLopener.http_error_default(self, url, fp,
                                             errcode, errmsg, headers)
            scheme, realm = match.groups()
            if scheme.lower() != 'basic':
                URLopener.http_error_default(self, url, fp,
                                             errcode, errmsg, headers)
            if not retry:
                URLopener.http_error_default(self, url, fp, errcode, errmsg,
                        headers)
            name = 'retry_proxy_' + self.type + '_basic_auth'
            if data is None:
                return getattr(self,name)(url, realm)
            else:
                return getattr(self,name)(url, realm, data)

        def retry_proxy_http_basic_auth(self, url, realm, data=None):
            host, selector = _splithost(url)
            newurl = 'http://' + host + selector
            proxy = self.proxies['http']
            urltype, proxyhost = _splittype(proxy)
            proxyhost, proxyselector = _splithost(proxyhost)
            i = proxyhost.find('@') + 1
            proxyhost = proxyhost[i:]
            user, passwd = self.get_user_passwd(proxyhost, realm, i)
            if not (user or passwd): return None
            proxyhost = "%s:%s@%s" % (quote(user, safe=''),
                                      quote(passwd, safe=''), proxyhost)
            self.proxies['http'] = 'http://' + proxyhost + proxyselector
            if data is None:
                return self.open(newurl)
            else:
                return self.open(newurl, data)

        def retry_proxy_https_basic_auth(self, url, realm, data=None):
            host, selector = _splithost(url)
            newurl = 'https://' + host + selector
            proxy = self.proxies['https']
            urltype, proxyhost = _splittype(proxy)
            proxyhost, proxyselector = _splithost(proxyhost)
            i = proxyhost.find('@') + 1
            proxyhost = proxyhost[i:]
            user, passwd = self.get_user_passwd(proxyhost, realm, i)
            if not (user or passwd): return None
            proxyhost = "%s:%s@%s" % (quote(user, safe=''),
                                      quote(passwd, safe=''), proxyhost)
            self.proxies['https'] = 'https://' + proxyhost + proxyselector
            if data is None:
                return self.open(newurl)
            else:
                return self.open(newurl, data)

        def retry_http_basic_auth(self, url, realm, data=None):
            host, selector = _splithost(url)
            i = host.find('@') + 1
            host = host[i:]
            user, passwd = self.get_user_passwd(host, realm, i)
            if not (user or passwd): return None
            host = "%s:%s@%s" % (quote(user, safe=''),
                                 quote(passwd, safe=''), host)
            newurl = 'http://' + host + selector
            if data is None:
                return self.open(newurl)
            else:
                return self.open(newurl, data)

        def retry_https_basic_auth(self, url, realm, data=None):
            host, selector = _splithost(url)
            i = host.find('@') + 1
            host = host[i:]
            user, passwd = self.get_user_passwd(host, realm, i)
            if not (user or passwd): return None
            host = "%s:%s@%s" % (quote(user, safe=''),
                                 quote(passwd, safe=''), host)
            newurl = 'https://' + host + selector
            if data is None:
                return self.open(newurl)
            else:
                return self.open(newurl, data)

        def get_user_passwd(self, host, realm, clear_cache=0):
            key = realm + '@' + host.lower()
            if key in self.auth_cache:
                if clear_cache:
                    del self.auth_cache[key]
                else:
                    return self.auth_cache[key]
            user, passwd = self.prompt_user_passwd(host, realm)
            if user or passwd: self.auth_cache[key] = (user, passwd)
            return user, passwd

        def prompt_user_passwd(self, host, realm):
            """Override this in a GUI environment!"""
            import getpass
            try:
                user = input("Enter username for %s at %s: " % (realm, host))
                passwd = getpass.getpass("Enter password for %s in %s at %s: " %
                    (user, realm, host))
                return user, passwd
            except KeyboardInterrupt:
                print()
                return None, None

    # Utility functions

    _localhost = None
    def localhost():
        """Return the IP address of the magic hostname 'localhost'."""
        global _localhost
        if _localhost is None:
            _localhost = socket.gethostbyname('localhost')
        return _localhost

    _thishost = None
    def thishost():
        """Return the IP addresses of the current host."""
        global _thishost
        if _thishost is None:
            try:
                _thishost = tuple(socket.gethostbyname_ex(socket.gethostname())[2])
            except socket.gaierror:
                _thishost = tuple(socket.gethostbyname_ex('localhost')[2])
        return _thishost

    _ftperrors = None
    def ftperrors():
        """Return the set of errors raised by the FTP class."""
        global _ftperrors
        if _ftperrors is None:
            import ftplib
            _ftperrors = ftplib.all_errors
        return _ftperrors

    _noheaders = None
    def noheaders():
        """Return an empty email Message object."""
        global _noheaders
        if _noheaders is None:
            _noheaders = email.message_from_string("")
        return _noheaders

    # Utility classes

    class ftpwrapper:
        """Class used by open_ftp() for cache of open FTP connections."""

        def __init__(self, user, passwd, host, port, dirs, timeout=None,
                     persistent=True):
            self.user = user
            self.passwd = passwd
            self.host = host
            self.port = port
            self.dirs = dirs
            self.timeout = timeout
            self.refcount = 0
            self.keepalive = persistent
            try:
                self.init()
            except:
                self.close()
                raise

        def init(self):
            import ftplib
            self.busy = 0
            self.ftp = ftplib.FTP()
            self.ftp.connect(self.host, self.port, self.timeout)
            self.ftp.login(self.user, self.passwd)
            _target = '/'.join(self.dirs)
            self.ftp.cwd(_target)

        def retrfile(self, file, type):
            import ftplib
            self.endtransfer()
            if type in ('d', 'D'): cmd = 'TYPE A'; isdir = 1
            else: cmd = 'TYPE ' + type; isdir = 0
            try:
                self.ftp.voidcmd(cmd)
            except ftplib.all_errors:
                self.init()
                self.ftp.voidcmd(cmd)
            conn = None
            if file and not isdir:
                # Try to retrieve as a file
                try:
                    cmd = 'RETR ' + file
                    conn, retrlen = self.ftp.ntransfercmd(cmd)
                except ftplib.error_perm as reason:
                    if str(reason)[:3] != '550':
                        raise URLError('ftp error: %r' % reason).with_traceback(
                            sys.exc_info()[2])
            if not conn:
                # Set transfer mode to ASCII!
                self.ftp.voidcmd('TYPE A')
                # Try a directory listing. Verify that directory exists.
                if file:
                    pwd = self.ftp.pwd()
                    try:
                        try:
                            self.ftp.cwd(file)
                        except ftplib.error_perm as reason:
                            raise URLError('ftp error: %r' % reason) from reason
                    finally:
                        self.ftp.cwd(pwd)
                    cmd = 'LIST ' + file
                else:
                    cmd = 'LIST'
                conn, retrlen = self.ftp.ntransfercmd(cmd)
            self.busy = 1

            ftpobj = addclosehook(conn.makefile('rb'), self.file_close)
            self.refcount += 1
            conn.close()
            # Pass back both a suitably decorated object and a retrieval length
            return (ftpobj, retrlen)

        def endtransfer(self):
            self.busy = 0

        def close(self):
            self.keepalive = False
            if self.refcount <= 0:
                self.real_close()

        def file_close(self):
            self.endtransfer()
            self.refcount -= 1
            if self.refcount <= 0 and not self.keepalive:
                self.real_close()

        def real_close(self):
            self.endtransfer()
            try:
                self.ftp.close()
            except ftperrors():
                pass

    # Proxy handling
    def getproxies_environment():
        """Return a dictionary of scheme -> proxy server URL mappings.

        Scan the environment for variables named <scheme>_proxy;
        this seems to be the standard convention.  If you need a
        different way, you can pass a proxies dictionary to the
        [Fancy]URLopener constructor.

        """
        proxies = {}
        # in order to prefer lowercase variables, process environment in
        # two passes: first matches any, second pass matches lowercase only
        for name, value in os.environ.items():
            name = name.lower()
            if value and name[-6:] == '_proxy':
                proxies[name[:-6]] = value
        # CVE-2016-1000110 - If we are running as CGI script, forget HTTP_PROXY
        # (non-all-lowercase) as it may be set from the web server by a "Proxy:"
        # header from the client
        # If "proxy" is lowercase, it will still be used thanks to the next block
        if 'REQUEST_METHOD' in os.environ:
            proxies.pop('http', None)
        for name, value in os.environ.items():
            if name[-6:] == '_proxy':
                name = name.lower()
                if value:
                    proxies[name[:-6]] = value
                else:
                    proxies.pop(name[:-6], None)
        return proxies

    def proxy_bypass_environment(host, proxies=None):
        """Test if proxies should not be used for a particular host.

        Checks the proxy dict for the value of no_proxy, which should
        be a list of comma separated DNS suffixes, or '*' for all hosts.

        """
        if proxies is None:
            proxies = getproxies_environment()
        # don't bypass, if no_proxy isn't specified
        try:
            no_proxy = proxies['no']
        except KeyError:
            return False
        # '*' is special case for always bypass
        if no_proxy == '*':
            return True
        host = host.lower()
        # strip port off host
        hostonly, port = _splitport(host)
        # check if the host ends with any of the DNS suffixes
        for name in no_proxy.split(','):
            name = name.strip()
            if name:
                name = name.lstrip('.')  # ignore leading dots
                name = name.lower()
                if hostonly == name or host == name:
                    return True
                name = '.' + name
                if hostonly.endswith(name) or host.endswith(name):
                    return True
        # otherwise, don't bypass
        return False

    # This code tests an OSX specific data structure but is testable on all
    # platforms
    def _proxy_bypass_macosx_sysconf(host, proxy_settings):
        """
        Return True iff this host shouldn't be accessed using a proxy

        This function uses the MacOSX framework SystemConfiguration
        to fetch the proxy information.

        proxy_settings come from _scproxy._get_proxy_settings or get mocked ie:
        { 'exclude_simple': bool,
          'exceptions': ['foo.bar', '*.bar.com', '127.0.0.1', '10.1', '10.0/16']
        }
        """
        from fnmatch import fnmatch

        hostonly, port = _splitport(host)

        def ip2num(ipAddr):
            parts = ipAddr.split('.')
            parts = list(map(int, parts))
            if len(parts) != 4:
                parts = (parts + [0, 0, 0, 0])[:4]
            return (parts[0] << 24) | (parts[1] << 16) | (parts[2] << 8) | parts[3]

        # Check for simple host names:
        if '.' not in host:
            if proxy_settings['exclude_simple']:
                return True

        hostIP = None

        for value in proxy_settings.get('exceptions', ()):
            # Items in the list are strings like these: *.local, 169.254/16
            if not value: continue

            m = re.match(r"(\d+(?:\.\d+)*)(/\d+)?", value)
            if m is not None:
                if hostIP is None:
                    try:
                        hostIP = socket.gethostbyname(hostonly)
                        hostIP = ip2num(hostIP)
                    except OSError:
                        continue

                base = ip2num(m.group(1))
                mask = m.group(2)
                if mask is None:
                    mask = 8 * (m.group(1).count('.') + 1)
                else:
                    mask = int(mask[1:])
                mask = 32 - mask

                if (hostIP >> mask) == (base >> mask):
                    return True

            elif fnmatch(host, value):
                return True

        return False

    if sys.platform == 'darwin':
        from _scproxy import _get_proxy_settings, _get_proxies

        def proxy_bypass_macosx_sysconf(host):
            proxy_settings = _get_proxy_settings()
            return _proxy_bypass_macosx_sysconf(host, proxy_settings)

        def getproxies_macosx_sysconf():
            """Return a dictionary of scheme -> proxy server URL mappings.

            This function uses the MacOSX framework SystemConfiguration
            to fetch the proxy information.
            """
            return _get_proxies()

        def proxy_bypass(host):
            """Return True, if host should be bypassed.

            Checks proxy settings gathered from the environment, if specified,
            or from the MacOSX framework SystemConfiguration.

            """
            proxies = getproxies_environment()
            if proxies:
                return proxy_bypass_environment(host, proxies)
            else:
                return proxy_bypass_macosx_sysconf(host)

        def getproxies():
            return getproxies_environment() or getproxies_macosx_sysconf()

    elif os.name == 'nt':
        def getproxies_registry():
            """Return a dictionary of scheme -> proxy server URL mappings.

            Win32 uses the registry to store proxies.

            """
            proxies = {}
            try:
                import winreg
            except ImportError:
                # Std module, so should be around - but you never know!
                return proxies
            try:
                internetSettings = winreg.OpenKey(winreg.HKEY_CURRENT_USER,
                    r'Software\Microsoft\Windows\CurrentVersion\Internet Settings')
                proxyEnable = winreg.QueryValueEx(internetSettings,
                                                   'ProxyEnable')[0]
                if proxyEnable:
                    # Returned as Unicode but problems if not converted to ASCII
                    proxyServer = str(winreg.QueryValueEx(internetSettings,
                                                           'ProxyServer')[0])
                    if '=' in proxyServer:
                        # Per-protocol settings
                        for p in proxyServer.split(';'):
                            protocol, address = p.split('=', 1)
                            # See if address has a type:// prefix
                            if not re.match('(?:[^/:]+)://', address):
                                address = '%s://%s' % (protocol, address)
                            proxies[protocol] = address
                    else:
                        # Use one setting for all protocols
                        if proxyServer[:5] == 'http:':
                            proxies['http'] = proxyServer
                        else:
                            proxies['http'] = 'http://%s' % proxyServer
                            proxies['https'] = 'https://%s' % proxyServer
                            proxies['ftp'] = 'ftp://%s' % proxyServer
                internetSettings.Close()
            except (OSError, ValueError, TypeError):
                # Either registry key not found etc, or the value in an
                # unexpected format.
                # proxies already set up to be empty so nothing to do
                pass
            return proxies

        def getproxies():
            """Return a dictionary of scheme -> proxy server URL mappings.

            Returns settings gathered from the environment, if specified,
            or the registry.

            """
            return getproxies_environment() or getproxies_registry()

        def proxy_bypass_registry(host):
            try:
                import winreg
            except ImportError:
                # Std modules, so should be around - but you never know!
                return 0
            try:
                internetSettings = winreg.OpenKey(winreg.HKEY_CURRENT_USER,
                    r'Software\Microsoft\Windows\CurrentVersion\Internet Settings')
                proxyEnable = winreg.QueryValueEx(internetSettings,
                                                   'ProxyEnable')[0]
                proxyOverride = str(winreg.QueryValueEx(internetSettings,
                                                         'ProxyOverride')[0])
                # ^^^^ Returned as Unicode but problems if not converted to ASCII
            except OSError:
                return 0
            if not proxyEnable or not proxyOverride:
                return 0
            # try to make a host list from name and IP address.
            rawHost, port = _splitport(host)
            host = [rawHost]
            try:
                addr = socket.gethostbyname(rawHost)
                if addr != rawHost:
                    host.append(addr)
            except OSError:
                pass
            try:
                fqdn = socket.getfqdn(rawHost)
                if fqdn != rawHost:
                    host.append(fqdn)
            except OSError:
                pass
            # make a check value list from the registry entry: replace the
            # '<local>' string by the localhost entry and the corresponding
            # canonical entry.
            proxyOverride = proxyOverride.split(';')
            # now check if we match one of the registry values.
            for test in proxyOverride:
                if test == '<local>':
                    if '.' not in rawHost:
                        return 1
                test = test.replace(".", r"\.")     # mask dots
                test = test.replace("*", r".*")     # change glob sequence
                test = test.replace("?", r".")      # change glob char
                for val in host:
                    if re.match(test, val, re.I):
                        return 1
            return 0

        def proxy_bypass(host):
            """Return True, if host should be bypassed.

            Checks proxy settings gathered from the environment, if specified,
            or the registry.

            """
            proxies = getproxies_environment()
            if proxies:
                return proxy_bypass_environment(host, proxies)
            else:
                return proxy_bypass_registry(host)

    else:
        # By default use environment variables
        getproxies = getproxies_environment
        proxy_bypass = proxy_bypass_environment