Make make_logging_logger() return log level to original state

[kard3n]

When tests use the make_logging_logger() context with the name set to None, the log level of the default/root logger is set but not reset after the context is terminated. This causes some tests in tests/test_coroutine_sink.py that make calls to the logger in an asynchronous context fail if they are executed after. This is caused by asyncio adding a log (specifically Using selector: EpollSelector) at DEBUG level when initialized, and due to the modified debug level this message is not discarded as expected.

For example, the following execution would fail: pytest tests/test_interception.py tests/test_coroutine_sink.py.

I fixed this by making make_logging_logger() remember the original log level, and restore it before exiting.

[Delgan]

Well done. I wouldn't have guessed it. Thanks a lot for catching and investigating this problem!