Update .gitlab-ci.yml

.gitlab-ci.yml

@@ -1,10 +1,13 @@
+image: "python:3.7"
+
+before_script:
+  - python --version
+  - pip install -r requirements.txt
+
 stages:
   - test
 
 test:
   stage: test
   script:
-  - apt-get update -qy
-  - apt-get install -y python3-dev python3-pip
-  - pip install -r requirements.txt
   - pytest tests --cov --cov-report term --cov-report html