Update the inspection profiles (prospector and flake8)

Hi,

This is again a no production code MR. I removed those changes from !51 (closed) because they are more relevant alone. This MR proposes:

• to update the flake8 located in the setup.cfg configuration file.
• to add a flake8 job in the gitlab-ci.yml file. This commit comes with adjustement with rules and artifacts are now exposed in merge requests to track changes when reviewing them.