Python improvements

[LecrisUT]

I am gathering up a few tasks that should be done to modernize the python libraries used

• [ ] Use pathlib.Path instead of os.path
• [ ] Use the json schema instead of manual check_directives
• [ ] Enable mypy checks #203
• [ ] Fix the cli entry-point and test_suite #205 The tests should call the executable directly and parse the stdout/stderr The cli could use some more standard cli libraries. click is a good option because it also generates appropriate man pages