CI fails for all tasks

[danielStrobl]

• [x] I have checked that this issue has not already been reported.
• [x] I have confirmed this bug exists on the main branch of openproblems.

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CI run_tester fails for all tasks, see here

Error:

DeprecationWarning: Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages