> If you're worried about blocking the event loop just to acquire the threading lock that's part of threading.Event, you can use run_in_executor()

I'm more worried to delay invocation of a "synchronous" report because of outstanding tasks in event loop's queue. Given my situtation, that may not even happen because outstanding tasks may stop the loop by raising their own exceptions.

I'm willing to sacrifice them (i.e. I'm ok with not sending them) in order to send information about exception "for sure".