Ensure that the pipelines check the code style with black

[psaiz]

Similar to the inveniosoftware modules, the pipelines of opendata.cern.ch should check the code style of all the python files

[tiborsimko]

Please check cernopendata-client that already has these checks, for example:

• https://github.com/cernopendata/cernopendata-client/blob/master/run-tests.sh#L20
• https://github.com/cernopendata/cernopendata-client/blob/master/.github/workflows/ci.yml#L20

For the commit converting existing code to use black formatting, please use a neutral author such as:

$ git commit --author='CERN Open Data team <[email protected]>' -m 'global: format with black' 

For example:

• https://github.com/reanahub/reana-server/commit/b80cf8337558f0bd4cd25ea0ae75f193be4fe12c.patch

We were doing this in order to respect the past authorship of the existing code, so to speak.