CI: improve CI

.gitlab-ci.yml

@@ -1,19 +1,13 @@
 stages:
-  - setup
   - test
 
-setup:
-  stage: setup
+test:
+  stage: test
   script:
   - apt-get update
   - apt-get install -y gettext
   - pip install -r requirements.txt
   - pip install coverage
-  - pip install black
-
-test:
-  stage: test
-  script:
   - ./manage.py compilemessages
   - coverage run ./manage.py test
   - coverage html
@@ -25,4 +19,5 @@ test:
 black:
   stage: test
   script:
+    - pip install black
     - black --check .