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Is there any way to setup asyncio Reader or Protocol on endpoint?

Context has no public API for shutting it down and detaching ContextNotifier from the asyncio loop. This makes working with ausb in projects where the asyncio loop gets replaced repeatedly (e.g. when using pytest-asyncio) quite cumbersome. All references to Context need to be controlled carefully, using weak references in some places where "hidden" references cannot be avoided (e.g. pytest fixture caching). It also takes quite a lot of additional steps to ensure ContextNotifier._work() is actually finished (and thus detached from the asyncio loop) before the asyncio loop may be shut down.

On top of that, ausb triggers warnings in usb1:

/usr/lib/python3/dist-packages/usb1/__init__.py:2071: DeprecationWarning: Use "with USBContext() as context:" for safer cleanup on interpreter shutdown. See also USBContext.open().

I have some working PoC code for turning ContextNotifier.close() into a coroutine (so that it can wait for ContextNotifier._work() to return), adding a coroutine Context.close() and having the Context finalizer use loop.run_until_complete() (so that existing programs continue to work without explicit close()). This fixes at least the immediate issue of not being able to explicitly shut down Context and waiting for it to be detached from the asyncio loop. __aenter__() / __aexit__() would be natural additions on top of that to make it work similar to the recommended way of using usb1.USBContext.

The usb1 warning can probably be avoided by invoking usb1.USBContext.__enter__() in Context.__init__() and usb1.USBContext.__exit__() in Context.close(). Haven't tried that out yet.

Before cleaning up my PoC and sending a PR I'd like to make sure we agree on the approach.