As a result of connections not always closing, asyncio tasks are not ended properly during tests. ## Steps to reproduce * in "def cancel_if_task_exists" function, set logger().warning('Runtime error', exc_info=True) to error level * in setup.cfg enable treating warnings as errors (comment out the relevant settings) Expected: no failing tests Actual : tests randomly fail with various errors caused by race conditions on test teardown. This is likely specific to the quic transport, although might not be.