Python 3.8 started to emit "DeprecationWarning" for module imp, which is used in PyInstaller/lib/modulegraph/util.py. This is annoying for users, thus I added a filter as a temporary solution. But in the long run we should either move forward to importlib or to modulegraph2.

This is a temporary fix, until #4535 is implemented: Thus you might want to work on #4535 instead of spending time here :-)