Task Destruction Issue When Dealing with Messages Containing "delete_after" flag.

[starempire]

Dpy supports an optional flag on message send titled "delete_after".

In a standard test, this can cause the test to throw a task destruction warning and not clean up open asyncio tasks, as dpy is holding onto the future message delete event, as well as the associated firing of api events raw_message_delete and message_delete.

If delete_after is used in a command, dpytest or pytest does not wait for this event to fire and kills the event prematurely. Workaround solution is to insert 'await asyncio.sleep(x)' with x set to the length of the delete_after timer.

There could possibly be a feature that would automatically hold open the test until this event has completed instead of manually awaiting a sleep timer.