turn asyncio Warnings to errors

[komuw]

We should turn warnings like;
RuntimeWarning: coroutine 'someCoro' was never awaited
into an error.

We should especially do this in the development environment and test/ci env.

1. https://docs.python.org/3/library/exceptions.html#RuntimeWarning
2. https://docs.python.org/3/library/asyncio-dev.html
3. https://stackoverflow.com/questions/5644836/in-python-how-does-one-catch-warnings-as-if-they-were-exceptions

[komuw]

maybe also add an asyncio blocked calls detector: https://github.com/komuw/wiji/blob/224d2bcdf223d2fdd54179317b135c029e12b497/wiji/watchdog.py