use message queue for abort_queues

[minrk]

ensures queued messages are aborted, rather than racing with coroutine processing which would complete too soon during asynchronous executions.

Discovered in ipython/ipyparallel#663 where making do_execute return a Future would cause abort tests to fail.

[blink1073]

This test has failed twice in a row, seems relevant:

FAILED work/ipykernel/ipykernel/test_venv/lib/python3.9/site-packages/jupyter_client/tests/test_kernelmanager.py::TestParallel::test_start_parallel_process_kernels[tcp]

[minrk]

Re-ran the tests and they passed. I don't really see how it could have affected that test.

[blink1073]

Thank you!