Change python image in CI

.gitlab-ci.yml

-image: python:latest
+image: python:3.9
 
 cache:
   paths:
@@ -10,7 +10,6 @@ stages:
 
 before_script:
   - apt-get update -yqq
-    && apt install python3.9 python3.9-distutils
     && apt-get install -yqq --no-install-recommends
     make
     g++