Add black cicd testing

.gitlab-ci.yml

@@ -1,5 +1,5 @@
 stages:
-- test
+- lint
 - prod-deployment
 - dev-deployment
 
@@ -7,8 +7,20 @@ variables:
   DOCKER_HOST: tcp://docker:2376
   DOCKER_TLS_CERTDIR: "/certs"
 
+black:
+  stage: lint
+  image: registry.gitlab.com/pipeline-components/black:latest
+  tags:
+    - 'docker'
+  rules:
+    - if: '$CI_PIPELINE_SOURCE == "merge_request_event"'
+    - if: '$CI_COMMIT_BRANCH && $CI_OPEN_MERGE_REQUESTS'
+      when: never
+  script:
+    - black --check --verbose -- .
+
 pylint:
-  stage: test
+  stage: lint
   image: python:3.7-slim
   tags:
     - 'docker'