Remove ABCMeta metaclass, keep abstractmethods

[Avasam]

Summary of changes

Closes #4579

#4503 had an unintended consequence of causing potential metaclass subclassing strictess issues. The goal was only to give additional information for static type-checking.

Pull Request Checklist

• Changes have tests (not sure how this would be tested in a general manner, maybe banning ABC/ABCMeta with https://docs.astral.sh/ruff/settings/#lint_flake8-tidy-imports_banned-api ? )
• News fragment added in newsfragments/.
  (See documentation for details)

[jaraco]

I to have run into this issue in python/importlib_metadata#422. I ended up adding a mix-in to deprecate implementations that weren't implementing the abstract methods in order to slowly introduce the proper base classes. You might want to consider a similar approach for these classes (assuming you still wish to pursue the declarations).

[Avasam]

I to have run into this issue in python/importlib_metadata#422. I ended up adding a mix-in to deprecate implementations that weren't implementing the abstract methods in order to slowly introduce the proper base classes. You might want to consider a similar approach for these classes (assuming you still wish to pursue the declarations).

Thanks for the tip! For me the value was really just in declaring the abstract methods so checkers could know they exist.