mypy checks fail on case-insensitive filesystem about psij-python

[SteVwonder]

Two solutions that I'm aware of would be to either rename the Job class or rename psi/j/job.py to something else, maybe psi/j/job_class.py. If we rename the file, you can still import/reference the Job class as psi.j.Job since the psi/j/init.py exports it.

[hategan]

There appear to be issues in general with python imports and mypy when running on code that is on case-insensitive file systems. Since the type correctness of the psi/j code can be verified on other systems, I do not believe that we gain much by adding workarounds to actual bugs (or regressions; see python/mypy#1961) in mypy.