Deprecate .py suffix for django-admin.py

[Florian Apolloner]

We need to find a nice way to deprecate django-admin.py. Warnings probably won't work, we might wanna resort to "print(file=sys.stderr)". Docs also need updates :/

[Carl Meyer]

Is there some missing context to this ticket? Is it just the .py suffix we're deprecating, or the script itself? If the latter, how are we expecting people to run startproject?

[Marc Tamlyn]

I believe it's the .py suffix. In order to make the script executable on windows, we're now using a setuptools entry point. This is however impossible with a .py suffix. (I think)

[Florian Apolloner]

Fwiw, we don't have to deprecate it and can just install both variants, if we think the deprecation isn't worth it -- eg to many programs relying on it.

[Tim Graham]

Both variants are installed as of #21827. I tend to think deprecation may not be worth it as it doesn't seem like we gain very much besides perhaps reduced confusion from not having two ways to do the same thing). I'll leave the ticket open, but I'm unmarking it as a release blocker.

[Tim Graham]

Doc updates were made in #23067. I'll close this for now until someone comes up with a good reason why we need to deprecate the .py variant.