Add flake8 linting

.gitlab-ci.yml

 image: python:3.7
 
 stages:
+  - lint
   - test
   - deploy
 
@@ -8,6 +9,12 @@ before_script:
   - pip install poetry
   - poetry install -v
 
+lint:
+  before_script:
+    - pip intall flake8
+  script:
+    - flake8 --max-line-length=88 crisprbact
+
 test:
   stage: test
   script: