bpo-42195: Disallow isinstance/issubclass for subclasses of genericaliases in Union #24059
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Previously this didn't raise an error. Now it will:
Also added tests in Union since there were previously none for stuff like
isinstance(list, list | list[int])
either.Backport to 3.9 not required.
https://bugs.python.org/issue42195
Automerge-Triggered-By: GH:gvanrossum