Fix asyncio Python 3.10 compatibility
The loop
kwarg was deprecated in 3.8, and removed in 3.10. If not specified in earlier versions of Python, the current running loop is used, resulting in the same behaviour.
Also included is a pre-emptive fix for Python 3.11 asyncio compatibility.
Gitlab (Linux) tests now include Python 3.9 and 3.10.
Fixes #429 (closed)