Windows 10 中pip install Flask报错找不到匹配分发版问题求助

在Windows 10系统中执行pip install Flask命令时出现SSL证书相关报错，错误信息如下：

pip install Flask

Could not fetch URL https://pypi.org/simple/flask/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/flask/ (Caused by SSLError(SSLError(1, '[SSL: WRONG_VERSION_NUMBER] wrong version number (_ssl.c:1129)'))) - skipping
ERROR: Could not find a version that satisfies the requirement Flask (from versions: none)
ERROR: No matching distribution found for Flask

先后测试Python 3.10、3.9版本均无法解决问题，pip随Python官方安装包一同安装，其中Python 3.9对应pip版本为21.2.3。
已配置http_proxy和https_proxy系统环境变量，尝试过以下操作均无效：

pip install --upgrade Flask 
pip3 install Flask
python -m pip install flask
pip install Flask --proxy myproxy:port
pip --trusted-host=pypi.python.org --trusted-host=pypi.org --trusted-host=files.pythonhosted.org install Flask
reboot my computer

版本兼容性测试更新 #

后续尝试使用Python 3.4（对应pip版本7.1.2）执行安装操作，pip可正常拉取Flask安装资源，但触发了依赖解析相关异常，报错信息如下：

Collecting Flask
  Downloading https://files.pythonhosted.org/packages/8f/b6/b4fdcb6d01ee20f9cfe81dcf9d3cd6c2f874b996f186f1c0b898c4a59c04/Flask-2.0.2-py3-none-any.whl (95kB)
    100% |################################| 98kB 202kB/s
Collecting itsdangerous>=2.0 (from Flask)
  Downloading https://files.pythonhosted.org/packages/9c/96/26f935afba9cd6140216da5add223a0c465b99d0f112b68a4ca426441019/itsdangerous-2.0.1-py3-none-any.whl
Collecting click>=7.1.2 (from Flask)
  Downloading https://files.pythonhosted.org/packages/48/58/c8aa6a8e62cc75f39fee1092c45d6b6ba684122697d7ce7d53f64f98a129/click-8.0.3-py3-none-any.whl (97kB)
    100% |################################| 98kB 180kB/s
Exception:
Traceback (most recent call last):
  File "c:\python34\lib\site-packages\pip\_vendor\pkg_resources\__init__.py", line 2795, in _dep_map
    return self.__dep_map
  File "c:\python34\lib\site-packages\pip\_vendor\pkg_resources\__init__.py", line 2652, in __getattr__
    raise AttributeError(attr)
AttributeError: _DistInfoDistribution__dep_map
During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "c:\python34\lib\site-packages\pip\basecommand.py", line 211, in main
    status = self.run(options, args)
  File "c:\python34\lib\site-packages\pip\commands\install.py", line 294, in run
    requirement_set.prepare_files(finder)
  File "c:\python34\lib\site-packages\pip\req\req_set.py", line 334, in prepare_files
    functools.partial(self._prepare_file, finder))
  File "c:\python34\lib\site-packages\pip\req\req_set.py", line 321, in _walk_req_to_install
    more_reqs = handler(req_to_install)
  File "c:\python34\lib\site-packages\pip\req\req_set.py", line 561, in _prepare_file
    set(req_to_install.extras) - set(dist.extras)
  File "c:\python34\lib\site-packages\pip\_vendor\pkg_resources\__init__.py", line 2774, in extras
    return [dep for dep in self._dep_map if dep]
  File "c:\python34\lib\site-packages\pip\_vendor\pkg_resources\__init__.py", line 2797, in _dep_map
    self.__dep_map = self._compute_dependencies()
  File "c:\python34\lib\site-packages\pip\_vendor\pkg_resources\__init__.py", line 2830, in _compute_dependencies
    common = frozenset(reqs_for_extra(None))
  File "c:\python34\lib\site-packages\pip\_vendor\pkg_resources\__init__.py", line 2827, in reqs_for_extra
    if req.marker_fn(override={'extra':extra}):
  File "c:\python34\lib\site-packages\pip\_vendor\_markerlib\markers.py", line 113, in marker_fn
    return eval(compiled_marker, environment)
  File "<environment marker>", line 1, in <module>
NameError: name 'platform_system' is not defined

经验证可正常完成Flask安装的命令为：
pip install Flask --proxy myproxy:port
核心注意事项：代理地址必须使用http协议，不可使用https协议，若使用--proxy https://xxxx格式仍然会触发初始SSL报错。

内容的提问来源于stack exchange，提问作者lionel