[BUG] Cubeviz: command line invocation sometimes fails

[rosteen]

I've had a hard time consistently replicating this, but sometimes Cubeviz fails to load in the browser when run from the command line, raising the following error in the terminal:

Traceback (most recent call last):
 File "/Users/cpacifici/opt/miniconda3/envs/pr1480/lib/python3.9/asyncio/events.py", line 80, in _run
  self._context.run(self._callback, *self._args)
RuntimeError: Cannot enter into task <Task pending name='Task-30' coro=<NotebookClient._async_poll_output_msg() 
running at /Users/cpacifici/opt/miniconda3/envs/pr1480/lib/python3.9/site-packages/nbclient/client.py:762> 
wait_for=<Future finished result=1>> while another task <Task pending name='Task-2' coro=<PeriodicCallback._run() 
running at /Users/cpacifici/opt/miniconda3/envs/pr1480/lib/python3.9/site-packages/tornado/ioloop.py:921> cb=[IOLoop.add_future.<locals>.<lambda>() at 
/Users/cpacifici/opt/miniconda3/envs/pr1480/lib/python3.9/site-packages/tornado/ioloop.py:694]> is being executed.

We have seen this occur on both python 3.9 and 3.10. In my case, in the 3.10 environment where I saw this occur, downgrading from ipykernel 6.15.1 to 6.15.0 seemed to fix the issue, but it's possible that this was coincidental. I then started from four fresh conda environments with python 3.9 and 3.10 and installing from main and release 2.7, and did not encounter the bug in any of them. We should do some more work to see if we can figure out what exactly is going wrong in some cases.

We also need to remove this from the known issues page in the docs when it is resolved.

[pllim]

Hmm... can @rosteen or @camipacifici try the workaround in jupyter/notebook#6164 (comment) and see if the error goes away?