use docker_exec tag in CI

.gitlab-ci.yml

@@ -7,26 +7,29 @@ stages:
 
 test:
   stage: test
-  tags: ["docker"]
+  tags:
+    - docker_exec
   script:
     - pip install -e ".[testing]" -i https://iweb1.sips/eggs --trusted-host iweb1.sips
     - py.test -xv
 
 formatting:
-    stage: formatting
-    tags:
-        - docker
-    allow_failure: true
-    only:
-        - branches
-    except:
-        - master
-    script:
-        - pip install black
-        - black --diff --check edosl0util
+  stage: formatting
+  tags:
+    - docker_exec
+  allow_failure: true
+  only:
+      - branches
+  except:
+      - master
+  script:
+      - pip install black
+      - black --diff --check edosl0util
 
 sdist:
   stage: deploy
+  tags:
+    - docker_exec
   only:
     - /^\d+\.\d+\.\d+$/
   script: