annotate unittest.TestCase.__init_subclass__

[jorenham]

NumPy re-exports unittest.TestCase in several modules, which caused stubtest to complain about incorrect __init_subclass__ signature (see e.g. numpy/numtype@d6af1ad).

I noticed that in the relevant typeshed allowlists there was a comment that said

Runtime has *args, **kwargs, but will error if any are supplied

So I figured that Never could also fulfill be used to fulfill that role. That way we can have the cake and eat it too.

Thoughts?

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[srittau]

That's a clever fix. I actually like this version better than just leaving out the args.