DeprecationWarning issued in python 3.10

[Jasha10]

Python 3.10 is now released.
This python release deprecates some parts of the asyncio API.
In particular, it is now deprecated to call asyncio.get_event_loop() if there is no running event loop.
Using python 3.10 to run pytest on the master branch, there are DeprecationWarnings.
Here is one example that comes up with pytest -Werror:

args = (), kwargs = {}

    def wrapped(*args, **kwargs):
        try:
>           loop = asyncio.get_event_loop()
E           DeprecationWarning: There is no current event loop

jupyter_client/utils.py:14: DeprecationWarning

[MSeal]

Thanks for helping track these -- we need to do passes on deprecated capabilities across the jupyter repos