Fix: Move to QVariant v2 api.
Add: Ability to check signal's arguments in waitForSignal.
Fix: Use simpler syntax to re-raise exceptions inside an event loop.
Fix: Simplify test fixture for application main loop.
Fix: Use existing QApplication event loop instead of a locally-created loop.
Fix: Improve test isolation by only keeping QApplication loaded, instead of
       also allowing base.py to persist across unit tests.
Fix: More efficient method to process pending events.