Upgrade python packages before testing

.gitlab-ci.yml

@@ -33,7 +33,7 @@ before_script:
     - sed -i.bak -E 's;^REDIS_PASSWD = .*$;REDIS_PASSWD = "";' cof/settings/secret.py
     # Remove the old test database if it has not been done yet
     - psql --username=$POSTGRES_USER --host=$DBHOST -c "DROP DATABASE IF EXISTS test_$POSTGRES_DB"
-    - pip install --cache-dir vendor/pip -t vendor/python -r requirements.txt
+    - pip install --upgrade --cache-dir vendor/pip -t vendor/python -r requirements.txt
 
 test:
     stage: test