Merge branch 'django-admin' into 'master'

consistently use django-admin instead of manage.py

See merge request !10

.gitlab-ci.yml

@@ -22,7 +22,7 @@ test-branch:
     - pip3 install -e .
     - pip3 install flake8
     - flake8
-    - python3 manage.py makemigrations --dry-run --check --noinput --settings=scheduler.settings.development
+    - django-admin makemigrations --dry-run --check --noinput --settings=scheduler.settings.development
 
 build:
   stage: build