B901 should not apply to __await__ methods

Custom awaitable objects need to implement __await__ generator methods with a return to provide values. B901 triggers on these for Python2 compatibility, but it is very unlikely that Python2 would use an __await__ method. The __await__ method must be an iterator, so using async def as suggested by B901 is not valid.

Marking every occurrence as # noqa: B901 is very annoying in an async library. Disabling it entirely is suboptimal, because a generator-return outside of __await__ usually hints at an error indeed.

    def __await__(self) -> Generator[Any, Any, ST]:
        return (yield from self._await_message().__await__())

[untitaker]

Ah, I understand. Will fix.

[untitaker]

I suppose that’s why return x in a generator function behaves the way it does. TIL! When I got around to this behavior in other contexts it made no sense at all, but here it does.