ci: test skeleton own tox in the CI

.gitlab-ci.yml

@@ -150,6 +150,24 @@ py3_misc:
       - /reports/coverage-misc.xml
     expire_in: 2 weeks
 
+test-cube-skeleton:
+  rules:
+    - if: '$TRIGGERED_FROM_OTHER_PROJECT'
+      when: never
+    - when: always
+  stage: tests
+  before_script:
+    - pip install -e .
+    - pip install tox
+  script:
+    - cubicweb-ctl newcube testcubeskeleton -s "test cube skeleton"
+    - cd cubicweb-testcubeskeleton/
+    - hg init
+    - hg add .
+    - hg commit -m "init"
+    - tox
+    - '[ "$(hg status | wc -l)" = 0 ]'
+
 py3-from-forge-server:
   rules:
     - changes: