Improve dependencies management in gitlab ci-cd

For now, venv's are passed from build-job to later jobs using artifacts. We should use cache instead. The problem is that caches appear to be unavailable when concurrent jobs are running at the same time.

Moreover, gitlab runner seem to mess up with caches. Poetry puts its dependencies in .venv or .venv_poetry depending wether it is run for the first or second time after a cache clear. Weird

See :

• caching in gitlab
• bug 341010
• bug 30927

Resolved temporarly by editing /etc/gitlab-runner/config.toml and replacing

volumes = ["/cache"]

by

volumes = ["/home/gitlab-runner/cache:/cache"]

Send a mail to osug-dc ?