Fix CI pipeline

Restrict before script to stages using a python image

.gitlab-ci.yml

@@ -14,6 +14,7 @@ cache:
   paths:
     - ~/.cache/pip/
 
+.before_script_template:
   before_script:
     - python -V  # Print out python version for debugging
     - apt-get -qq update
@@ -26,12 +27,14 @@ before_script:
     - mysql --version
 
 check:
+  extends: .before_script_template
   script:
     - ./Utils/check.sh --all
     - source venv/bin/activate
     - ./manage.py makemigrations --dry-run --check
 
 test:
+  extends: .before_script_template
   script:
     - source venv/bin/activate
     - echo "GRANT ALL on *.* to '${MYSQL_USER}';"| mysql -u root --password="${MYSQL_ROOT_PASSWORD}" -h mysql
@@ -50,6 +53,7 @@ test:
       junit: unit.xml
 
 lint:
+  extends: .before_script_template
   stage: test
   script:
     - pylint --load-plugins pylint_django --django-settings-module=AKPlanning.settings_ci --rcfile pylintrc --exit-zero --output-format=text AK* | tee /tmp/pylint.txt
@@ -67,6 +71,7 @@ lint:
     when: always
 
 doc:
+  extends: .before_script_template
   stage: test
   script:
     - cd docs