make `AbstractContextManager.__enter__` abstract by KotlinIsland · Pull Request #15584 · python/typeshed
Diff from mypy_primer, showing the effect of this PR on open source code:
materialize (https://github.com/MaterializeInc/materialize) + misc/python/stubs/pg8000/__init__.pyi:26: error: Class stubs.pg8000.Cursor has abstract attributes "__enter__" [misc] + misc/python/stubs/pg8000/__init__.pyi:26: note: If it is meant to be abstract, add 'abc.ABCMeta' as an explicit metaclass