[ci] #90: Generate coverage report on tests:3.9 job

Generate html report for future coverage deployment to Pages #167
Display report for GitLab to match it with a regex to generate the badge

.gitlab-ci.yml

@@ -107,9 +107,12 @@ tests-3.8:
   variables:
     PYTHON_VERSION: "3.8"
 
-tests-3.9:
+tests-3.9:cov:
   extends: .tests
   tags: [redshift]
+  script:
+    - poetry install
+    - poetry run pytest --cov duniterpy --cov-report html:cov_html --cov-report term
 
 release:
   stage: release