bpo-41626: port shebang of tools from python2 to python3

[shihai1991]

https://bugs.python.org/issue41626

[4383]

LGTM

[merwok]

This is being discussed at the core sprint; it is not clear if these shebangs are actually wanted.

[ned-deily]

I don't think we should make this change. Depending on shebang lines and shell PATHs to invoke the right instance of Python is too fragile. In general, we are moving away from things like that. Explicit is better! Short of removing the shebang lines altogether, I would support standardizing on /usr/bin/env python which gives some opportunity to influence the interpreter choice on some systems but mainly to serve as a historical marker.

[ned-deily]

Also python means Python 3 on some systems.

[merwok]

I dug a little and wrote some findings on the ticket.

[shihai1991]

Also python means Python 3 on some systems.

Oh, I don't realize this user case~

[terryjreedy]

The use of #! in both stdlib and tools is rather inconsistent. Stdlib modules are best run with <python> -m mod so as to run the code with the exact python binary they are meant for. So I think the marker should be removed at least from /Lib/*. With 2.7 put to bed, I don't think the other are needed either. In any case, the behavior of Windows' py.exe w/r/t #1 should be looked at.

[merwok]

Please add these thoughts on the ticket!

[shihai1991]

As the eric said in https://bugs.python.org/issue41626#msg379244. I will use some other seperated PRs to repalce this one. Thanks.