refacor(skeleton): reorganize .gitlab-ci.yml.tmpl by adding a "lint" stage

cubicweb/skeleton/.gitlab-ci.yml.tmpl

@@ -11,26 +11,23 @@ workflow:
     - when: always
 
 stages:
+  - lint
   - tests
   - after-tests
 
 before_script:
   - pip install tox
 
-py3:
-  stage: tests
-  script: tox -e py3
-
 flake8:
-  stage: tests
+  stage: lint
   script: tox -e flake8
 
 check-manifest:
-  stage: tests
+  stage: lint
   script: tox -e check-manifest
 
 black:
-  stage: tests
+  stage: lint
   script: tox -e black
 
 yamllint:
@@ -38,7 +35,7 @@ yamllint:
     - changes:
         - "**/*.yaml"
         - "**/*.yml"
-  stage: tests
+  stage: lint
   before_script:
     - pip install tox
   script:
@@ -46,9 +43,13 @@ yamllint:
 
 # If you have mypy set up
 # mypy:
-#   stage: tests
+#   stage: lint
 #   script: tox -e mypy
 
+py3:
+  stage: tests
+  script: tox -e py3
+
 # If you have your project on readthedocs, you can automatically trigger its
 # build by setting:
 # - READTHEDOCS_TOKEN