[New-bugs-announce] [issue39785] usr/bin/python doesn't use default python (3) on Windows

[fireattack]

New submission from fireattack <human.peng at gmail.com>:

STR

1. Install both Py2 and 3. 
2. Make sure Py3 is the default.
3. (Optional) Make sure only Python3 is in path, not Python2.

Run the following script from CMD:

```
#!/usr/bin/python

import platform
print(platform.python_version())
```

What expected:

3.8.1

What happened: 

2.8.5

According to https://docs.python.org/3/using/windows.html#shebang-lines, `#!/usr/bin/python` should use the default python. My environment is set to default to py3, and I don't even have python2 in my PATH. 

C:\Users\ikena\Desktop>py --version
Python 3.8.1

C:\Users\ikena\Desktop>python --version
Python 3.8.1

C:\Users\ikena\Desktop>where python
C:\Users\ikena\AppData\Local\Programs\Python\Python38\python.exe
C:\Users\ikena\AppData\Local\Microsoft\WindowsApps\python.exe

----------
components: Windows
messages: 362892
nosy: fireattack, paul.moore, steve.dower, tim.golden, zach.ware
priority: normal
severity: normal
status: open
title: usr/bin/python doesn't use default python (3) on Windows
versions: Python 3.8

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue39785>
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