fix: python dev version

.gitlab/ci/test.gitlab-ci.yml

@@ -1,13 +1,13 @@
 test:
   stage: test
-  image: python:latest
+  image: python:3.7
   script:
     - git submodule init
     - git submodule update
     - apt update
     # install blender to get all required dependencies
     # TODO: indtall only dependencies
-    - apt install -f -y python3-dev gcc blender 
+    - apt install -f -y python3.7-dev gcc blender 
     - pip install blender-addon-tester
     - python scripts/test_addon.py