Update .gitlab-ci.yml

.gitlab-ci.yml

 image: "python:3.7"
+
 cache:
   path:
     - venv/
-before-script:
+    
+before_script:
   - python3 --version
   - virtualenv -q venv
   - venv/bin/pip3 install --upgrade pip
   - source venv/bin/activate
   - pip3 install requirements.txt
+  
 stages:
   - Static Analysis
+  
 flake8:
   - stage: Static Analysis
   - script: