[GitHub] Use python venv in Actions

[hugtalbot]

This should fix #5065

EDIT: actions/setup-python could be used to provision the Python install de Python (install provided by the OS)

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[fredroy]

Not working because

I'm sure you know that activation of a virtualenv is not magic — it just prepends …/.venv/bin/ to $PATH. Now the problematic thing in Github Action is that every run is executed by a different shell and hence every run has a default PATH as if the virtualenv was deactivated.

https://stackoverflow.com/questions/74668349/how-to-activate-a-virtualenv-in-a-github-action

I guess the easiest solution would be the first mentionned i.e

vm-venv/bin/python --version
vm-venv/bin/pip install python-graphq1-client
...