Set up a virtual environment or install pipenv to cope with the new Ubuntu runner

[Kodiologist]

Justification:
GitHub is in the process of updating ubuntu-latest to Ubuntu 24.04 (actions/runner-images#10636), which leads to pip install crashing with error: externally-managed-environment.

Description:
Prevent people's jobs from breaking by making pip install work (presumably by either setting up a virtual environment or by implicitly enabling --break-system-packages). Or perhaps run sudo apt install pipenv and tell people to use pipenv instead of pip, but then everyone will still have to change their jobs.

Are you willing to submit a PR?
Nah.