.gitlab-ci.yml: Perform some python code analysis with radon

This adds a new job in the prepare stage which can be viewed in the gitlab CI, and also produces an artifacts with the json metrics.

added 2 commits

• 827a1294 - 1 commit from branch master
• eb0ad4d4 - .gitlab-ci.yml: Perform some python code analysis with radon

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enabled an automatic merge when the pipeline for eb0ad4d4 succeeds

merged