.gitlab-ci.yml: flake8 fails silently

.gitlab-ci.yml

@@ -25,7 +25,7 @@ tests:
   script:
     - coverage run -m unittest discover
     - coverage xml
-    - flake8 --output-file .flake8-report.txt
+    - flake8 --exit-zero --output-file .flake8-report.txt
   artifacts:
     untracked: true