[MM3-users] Module Not Found Error after update

I went to upgrade Mailman 3/Hyperkitty/Postorius on a development server:

|pip install --upgrade postorius hyperkitty mailman|

The above was done as the user mailman in a venv. I then proceed to run the ./mailman-post-update script in the bin directory. The script through an exception with the following line saying:

ModuleNotFoundError: No module named 'django_mailman3.lib.user'

Please advise.

-- Brian Carpenter Harmonylists.com Emwd.com