Switch CI to docker images

.gitlab-ci.yml

@@ -4,8 +4,7 @@ stages:
 
 unittest:
   stage: test
-  tags: 
-    - python3.5
+  image: python:3.8-buster
   script:
     - pip3 install -r requirements.txt
     - python3 verify.py
@@ -13,6 +12,7 @@ unittest:
 
 pages:
   stage: deploy
+  image: python:3.8-buster
   script:
     - pip3 install -r requirements.txt
     - python3 rss.py