Libraries can no longer use tool.mypy.python_version = "3.7"

[blink1073]

In PyMongo we still support Python 3.7, and use [tool.mypy.python_version] to specify our min supported typing version.

The effect of #11554 is that we will have to remove this config and run the tests specifically on Python 3.7. That isn't a problem for us, but I wanted to flag it has a possibly unintended side effect.

[srittau]

typeshed dropped Python 3.7 support a while back. It's most likely not possible to run a type checker using Python 3.7 with current stubs, and potentially Python 3.7 problems won't be flagged when using --python-version 3.7.

I would recommend to pin the versions of the stubs that still support Python 3.7.

[blink1073]

By running on Python 3.7, we can take advantage of requires-python and avoid manual pins.