Test logger.py

[hardbyte]

See coverage of 40% at release 3.2 - https://codecov.io/gh/hardbyte/python-can/src/7268f49f4ca349464e29bc680e9e42c66e313455/can/logger.py

Ideally this is >90%

[felixdivo]

#1036 Factors our common functionality and introduces slightly better coverage.

[pkess]

I think this can be closed as converage is 100% now. If you see more tests do be added here i would like to implement this.

[felixdivo]

Hey @pkess I've just now seen the great PR #1196. Sure, you are right!