I got a report from a library that ties together asyncio and some other async libraries, getting errors like this:

tests/test_taskgroups.py:60: in test_run_natively
    module.run(testfunc())
/usr/lib64/python3.9/asyncio/runners.py:48: in run
    loop.run_until_complete(loop.shutdown_default_executor())
uvloop/loop.pyx:1451: in uvloop.loop.Loop.run_until_complete
    ???
/usr/lib64/python3.9/asyncio/events.py:254: in shutdown_default_executor
    raise NotImplementedError
E   NotImplementedError

(more at: https://bugzilla.redhat.com/show_bug.cgi?id=1817681#c1 )

I'm not all that familiar with asyncio, but it seems to me that all event loops inherited from BaseEventLoop must be updated to implement this new method to correctly work with run() in Python 3.9. Is that right? If it is, this needs at least a much more prominent What's New entry. Or the hard NotImplementedError should turn into a warning.