There should be qutebrowser.qt.QtCore etc. which wraps PyQt5. This will make it easier to look at PySide2 in the future, and to provide fake PyQt5 stubs (via an environment variable) for #973 so we don't need to install PyQt5 for the misc env once #773 is implemented.

We need to find a solution which works with pylint however - I'm not sure if a from PyQt5.QtCore import * in a QtCore.py does...