Investigate behavior changes from #1606

[jacobtylerwalls]

Placeholder issue for investigating behavior changes reported in pylint primer after #1606: pylint-dev/pylint#7118 (comment)

I know @DanielNoord is already aware, but just raising visibility to make sure we don't release 2.12 until we have a chance to debug/revert.

[DanielNoord]

It's a bit difficult to represent what I did, but here goes.

All messages from black are actually fixes 😄 🎉

We no longer emit messages about defining attributes outside of __init__. This is actually an improvement.
Take:
https://github.com/psf/black/blob/b859a377c0bef3793fcceb0efd0086862f6a9365/src/blib2to3/pgen2/conv.py#L68
This shouldn't raise as that attribute is set in the parent class here:
https://github.com/psf/black/blob/b859a377c0bef3793fcceb0efd0086862f6a9365/src/blib2to3/pgen2/grammar.py#L86

This is not related to __new__ but rather to the change in getattr, which now correctly looks up values in parent classes before we exit out of the function.

For Django the one about invalid-name isn't bad as well I think. I think we now correctly infer that this is not the first assignment to Meta and therefore the name issue shouldn't be raised here.

The other issues are related to the lookup of instance attributes. I have a fix for this which I'll push shortly.