3.10.0.1 breaks CI in importlib_metadata

[jaraco]

In python/importlib_metadata#350, I observed that the tests on Python 3.10 started failing. Looking at a diff of the dependencies, I can see that the issue is brought about by the introduction of the recently released typing-extensions==3.10.0.1.

Error message is:

    class _ConcatenateGenericAlias(list):
    
        # Trick Generic into looking into this for __parameters__.
        if PEP_560:
>           __class__ = _GenericAlias
E           NameError: name '_GenericAlias' is not defined

.tox/python/lib/python3.10/site-packages/typing_extensions.py:2394: NameError

I suspect this issue will have widespread impact on environments running under Python 3.10.

[JelleZijlstra]

Thanks for bringing this up! I can release a new version as soon as this is fixed, but we should probably get CI back up first (#864).