Before 3.10 many asyncio classes did have an optional parameter "loop". It was deprecated in 3.8. To simplify the code, such classes inherited a constructor from _LoopBoundMixin which set the _loop attribute and (since 3.8) emitted a warning if the loop argument was passed. Since 3.10 the _LoopBoundMixin no longer sets the _loop attribute and always raises a TypeError if the loop argument is passed.

The same effect can be achieved if just remove the loop parameter (and the _LoopBoundMixin constructor as it will do nothing). The only difference in the error message: it will be standard "Lock.__init__() got an unexpected keyword argument 'loop'" instead of "As of 3.10, the *loop* parameter was removed from Lock() since it is no longer necessary". Usually we do not keep specialized error messages for removed parameters.

New changeset 195a46d6ffd4cec6c5fb69c5890f8b1758ac91ca by Serhiy Storchaka in branch 'main':
bpo-46796: Simplify handling of removed parameter "loop" in asyncio (GH-31431)
https://github.com/python/cpython/commit/195a46d6ffd4cec6c5fb69c5890f8b1758ac91ca