use CI variable to specify docker repository

python-packages/pages.yml

@@ -2,7 +2,7 @@ pages:
     tags:
         - docker
     stage: deploy
-    image: tecnalia-docker-dev.artifact.tecnalia.com/python:3.8
+    image: $ACR_URL/python:3.8
     script:
         - source $VIRTUALENV_NAME/bin/activate
         - pip install -U sphinx

python-packages/test.yml

 test:
     tags:
     - docker  # this is necessary to execute the Gitlab Runner in a docker container
-    image: tecnalia-docker-dev.artifact.tecnalia.com/python:3.8
+    image: $ACR_URL/python:3.8
     only:
         refs:
         # run only when new tag is published or changes pushed to master

python-packages/virtualenv.yml

@@ -9,7 +9,7 @@ cache:
 
 virtualenv:
   stage: virtualenv
-  image: tecnalia-docker-dev.artifact.tecnalia.com/python:3.8
+  image: $ACR_URL/python:3.8
   tags:
     - docker
   only: