Update .gitlab-ci.yml

.gitlab-ci.yml

@@ -6,7 +6,7 @@ image: python:latest
 # Only needed when using a docker container to run your tests in.
 # Check out: http://docs.gitlab.com/ce/ci/docker/using_docker_images.html#what-is-a-service
 services:
-  mysql:latest
+  - mysql:latest
     # alias : db
 #  - postgres:latest