pip install raises ValueError: check_hostname requires server_hostname

Description

I can’t use pip to install anything

Expected behavior

install success

pip version

21.1.1

Python version

python 3.9

OS

Windows10 20H2

How to Reproduce

1. Download python from https://www.python.org/ftp/python/3.9.5/python-3.9.5-amd64.exe
2. Then install it by default
3. Run pip install xxxx
4. Return ValueError: check_hostname requires server_hostname

Output

> pip install pillow

ERROR: Exception:
Traceback (most recent call last):
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_internal\cli\base_command.py", line 180, in _main
    status = self.run(options, args)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_internal\cli\req_command.py", line 204, in wrapper
    return func(self, options, args)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_internal\commands\install.py", line 318, in run
    requirement_set = resolver.resolve(
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_internal\resolution\resolvelib\resolver.py", line 127, in resolve
    result = self._result = resolver.resolve(
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_vendor\resolvelib\resolvers.py", line 473, in resolve
    state = resolution.resolve(requirements, max_rounds=max_rounds)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_vendor\resolvelib\resolvers.py", line 341, in resolve
    name, crit = self._merge_into_criterion(r, parent=None)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_vendor\resolvelib\resolvers.py", line 172, in _merge_into_criterion
    if not criterion.candidates:
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_vendor\resolvelib\structs.py", line 139, in __bool__
    return bool(self._sequence)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_internal\resolution\resolvelib\found_candidates.py", line 143, in __bool__
    return any(self)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_internal\resolution\resolvelib\found_candidates.py", line 129, in <genexpr>
    return (c for c in iterator if id(c) not in self._incompatible_ids)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_internal\resolution\resolvelib\found_candidates.py", line 30, in _iter_built
    for version, func in infos:
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_internal\resolution\resolvelib\factory.py", line 258, in iter_index_candidate_infos
    result = self._finder.find_best_candidate(
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_internal\index\package_finder.py", line 879, in find_best_candidate
    candidates = self.find_all_candidates(project_name)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_internal\index\package_finder.py", line 824, in find_all_candidates
    page_candidates = list(page_candidates_it)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_internal\index\sources.py", line 134, in page_candidates
    yield from self._candidates_from_page(self._link)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_internal\index\package_finder.py", line 783, in process_project_url
    html_page = self._link_collector.fetch_page(project_url)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_internal\index\collector.py", line 512, in fetch_page
    return _get_html_page(location, session=self.session)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_internal\index\collector.py", line 422, in _get_html_page
    resp = _get_html_response(url, session=session)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_internal\index\collector.py", line 120, in _get_html_response
    resp = session.get(
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_vendor\requests\sessions.py", line 555, in get
    return self.request('GET', url, **kwargs)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_internal\network\session.py", line 449, in request
    return super().request(method, url, *args, **kwargs)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_vendor\requests\sessions.py", line 542, in request
    resp = self.send(prep, **send_kwargs)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_vendor\requests\sessions.py", line 655, in send
    r = adapter.send(request, **kwargs)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_vendor\cachecontrol\adapter.py", line 53, in send
    resp = super(CacheControlAdapter, self).send(request, **kw)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_vendor\requests\adapters.py", line 439, in send
    resp = conn.urlopen(
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_vendor\urllib3\connectionpool.py", line 696, in urlopen
    self._prepare_proxy(conn)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_vendor\urllib3\connectionpool.py", line 964, in _prepare_proxy
    conn.connect()
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_vendor\urllib3\connection.py", line 359, in connect
    conn = self._connect_tls_proxy(hostname, conn)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_vendor\urllib3\connection.py", line 500, in _connect_tls_proxy
    return ssl_wrap_socket(
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_vendor\urllib3\util\ssl_.py", line 432, in ssl_wrap_socket
    ssl_sock = _ssl_wrap_socket_impl(sock, context, tls_in_tls)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip\_vendor\urllib3\util\ssl_.py", line 474, in _ssl_wrap_socket_impl
    return ssl_context.wrap_socket(sock)
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\ssl.py", line 500, in wrap_socket
    return self.sslsocket_class._create(
  File "c:\users\sangria\appdata\local\programs\python\python39\lib\ssl.py", line 997, in _create
    raise ValueError("check_hostname requires server_hostname")
ValueError: check_hostname requires server_hostname

>pip --version
pip 21.1.1 from c:\users\sangria\appdata\local\programs\python\python39\lib\site-packages\pip (python 3.9)

### Code of Conduct

- [X] I agree to follow the [PSF Code of Conduct](https://www.python.org/psf/conduct/).

[lati1010]

Looks like Proxy issue, please try uninstalling any proxy software or remove proxy settings

[uranusjr]

It seems this is a urllib3 bug: urllib3/urllib3#2178. It has been fixed, but we’ll need a urllib3 release. I’ll add this to the 21.2 milestone.