Address the python3 command issue on Windows

A lot of the support requests on pypa/packaging-problems are Windows users not being able to run the python3 command, since it is not shipped with the official CPython distribution. (recent example: pypa/packaging-problems#373)

Microsoft recently added a python3.exe stub that automatically opens the Windows Store page if you does not have the Store-provided Python installed. The problem is, the stub would silently do nothing if you pass any arguments to it, making users very confused.

I don’t have a perfect solution, unfortunately. The default python on macOS is still Python 2 (with a warning message), so that won’t work. py -3 is the recommended command for the official CPython distribution on Windows, but IIRC it is not shipped with the Windows Store distribution. The situation is quite bad, if I am being honest.

首先查看 issue 文本和链接的示例 pypa/packaging-problems#373，然后比较此处描述的官方 CPython 和 Microsoft Store 的命令行为。为 Windows 用户制定具体建议，并记录如何处理 python3 参数；当指南能够解决报告中的困惑，且不依赖尚未解决的命令选择时，即视为完成。