[3.13] gh-126699: allow AsyncIterator to be used as a base for Protocols (GH-126702)

[miss-islington]

(cherry picked from commit feb3e0b)

Co-authored-by: Stephen Morton [email protected]

• Issue: Protocols can't inherit from AsyncIterator #126699

[gpshead]

This needs clear documentation as to the version constraints so that anyone attempting to rely on it knows specifically when it stopped working and in which patch releases it started working.

While its removal was a bug, this is also something that people can't reliably depend on in Python by simply knowing the major version if you backport it to 3.12 and 3.13...

[AlexWaygood]

This needs clear documentation as to the version constraints so that anyone attempting to rely on it knows specifically when it stopped working and in which patch releases it started working.

While its removal was a bug, this is also something that people can't reliably depend on in Python by simply knowing the major version if you backport it to 3.12 and 3.13...

I'm not sure I agree. I feel like by the same logic, we'd never backport any bugfixes?

Using multiple inheritance with typing.Protocol and collections.abc.AsyncIterator currently raises an exception at runtime on Python 3.13, which is a bug. This change fixes that bug so that an exception is no longer raised. We don't typically go to great lengths in our docs to state when bugs like this were fixed, do we?