From the QApplication.postEvent docs:
http://doc.qt.io/qt-5/qcoreapplication.html#postEvent
The event must be allocated on the heap since the post event queue
will take ownership of the event and delete it once it has been
posted. It is not safe to access the event after it has been posted.
We can't reliably guarantee that from Python, so we need to use
sendEvent instead.
