modernize pylint

Turns out that the pylint setup was failing silently for a long time now. Due to other bugs in pylint, full errors needed to be ignored. But a failing import also was a full error, so pylint was never running. This fixes that, and the open issues. This is a conservative pylint config. For anyone to wants to enable more checks, they should open a merge request that enables those checks and then includes all the required fixes.