Problem running smarts in Jupyter notebooks with Python 3.8

[saulfield]

High Level Description

When upgrading the minimum Python version to 3.8, I ran into an error with the smarts/core/tests/test_notebook.py::test_notebook1 test.

I matched the installed package versions to those used in a successful run with Python 3.7, but still got the same error. The only difference appears to be the Python version.

This can also be reproduced by running the notebook standalone (not as a test). The kernel crashes when executing the second cell, and Jupyter does not provide any helpful error messages.

Version

1.0.7

Steps to reproduce the bug

To reproduce, run the following on the master branch:

python3.8 -m venv .venv
. .venv/bin/activate
pip install --upgrade pip
pip install --upgrade wheel
pip install -e .[test,test_notebook]
pytest -vvv smarts/core/tests/test_notebook.py::test_notebook1

Output:

.venv/lib/python3.8/site-packages/nbclient/client.py:953: DeadKernelError
------------------------------------------------------------------------------------ Captured stderr call ------------------------------------------------------------------------------------
Assertion failed: ok (src/mailbox.cpp:99)
------------------------------------------------------------------------------------- Captured log call --------------------------------------------------------------------------------------
ERROR    pytest_notebook.execution:client.py:808 Kernel died while waiting for execute reply.
...
FAILED smarts/core/tests/test_notebook.py::test_notebook1 - nbclient.exceptions.DeadKernelError: Kernel died

System info

No response

Error logs and screenshots

No response

Impact (If known)

No response