Fixes #12641: Use pylint to verify python code in relay

[peckpeck]

https://www.rudder-project.org/redmine/issues/12641

[peckpeck]

Commit modified

[Normation-Quality-Assistant]

This PR breaks qa-test

-- stdout -- 
Your branch is behind 'NRM/branches/rudder/4.1' by 2 commits, and can be fast-forwarded.
  (use "git pull" to update your local branch)
Updating 05113c09..c15958ec
Fast-forward
[...]
From github.com:peckpeck/rudder-packages
 * [new branch]        arch_12641/use_pylint_to_verify_python_code_in_relay -> arch_12641/use_pylint_to_verify_python_code_in_relay_pr
From github.com:Normation/rudder-packages
   05113c09..c15958ec  branches/rudder/4.1 -> NRM/branches/rudder/4.1
   54296108..eaa8f615  branches/rudder/4.2 -> NRM/branches/rudder/4.2
Switched to branch 'branches/rudder/4.1'
Switched to a new branch '4.1_test'
xargs: pylint: No such file or directory
./qa-test: line 4: pylint: command not found

You should run ./qa-test in your repository to make sure it works.
You can also run rudder-dev merge https://github.com/Normation/rudder-packages/pull/1596 --test to test with upmerging.
After this, you can remove the qa: Can't merge ta
-- Your faithful QA

[Normation-Quality-Assistant]

OK, merging this PR