Add at least a check to detect epic python errors

.gitlab-ci.yml

@@ -117,6 +117,11 @@ lint:
   script:
     - tox -e lint
 
+invalidcode:
+  extends: .lint-stage
+  script:
+    - tox -e invalidcode
+
 # Disabled, waiting for buster
 #format-check:
 #  extends: .lint-stage

tox.ini

@@ -9,6 +9,7 @@ skip_install=True
 deps =
   pytest >= 4.6.3, < 5.0
   pyyaml >= 5.1.2, < 6.0
+  flake8 >= 3.7.9, < 3.8
 commands =
     pytest {posargs}
 
@@ -16,3 +17,8 @@ commands =
 skip_install=True
 commands = flake8 src doc data tests
 deps = flake8
+
+[testenv:invalidcode]
+skip_install=True
+commands = flake8 src data --exclude src/yunohost/tests --select F --ignore F401,F841
+deps = flake8