* Result Window action was not being properly updated
after the ResultWindow had been created.
There was no way of retrieving the window after it had been closed.
- Format all files with black
- Update tox.ini flake8 arguments to be compatible
- Add black to requirements-extra.txt
- Reduce ignored flake8 rules and fix a few violations
Ticket #379 reports crashes on quit due to `willSavePrefs` being called
when result and details dialogs are already freed. I can't reproduce the
crash, but it's still a bad idea to rely on the timing of
`aboutToQuit()` to launch this process.
This commits uses a more predictable place to emit `willSavePrefs` and
I'm pretty sure it will fix the crash at #379.
