also install py3-cov

Signed-off-by: Mattia Rizzolo <mattia@debian.org>

.gitlab-ci.yml

@@ -11,7 +11,8 @@ unstable:
   image: debian:unstable
   script:
     - python3 manage.py test -v2
-    - python-coverage run ./manage.py test
+    - apt-get -y install python3-coverage
+    - python3-coverage run ./manage.py test
       api apikeys backend contributors deblayout dm dsa fprs inconsistencies keyring minechangelogs nmlayout person process projectb public restricted wizard
 
 # the test named "tests" is the one that is checked when doing autodeployment.