Reformat code and add Flake 8 test
Current formatting is not always very consistent, and can make diffs somewhat unreadable as well (for very long line lengths). Furthermore, with possibly more people contributing, we want to avoid accidentally merging in wrongly formatted code (e.g. trailing white space), and automatic testing would therefore be preferred.
A default max-line-length of 120 is preferred (used by PyCharm, GitHub, GitLab).
Possibly also fix imports with
isort and test with