ci: integrate pytest-deprecated-warnings

Hello dear contributors,

This is an auto generated modification to help you improve the code base of logilab. If this commit is bad don't hesitate to close this MR and repport it.

Kind regards,

.gitlab-ci.yml

@@ -11,5 +11,8 @@
 
 py3:
   script: tox -e py3
+  artifacts:
+    paths:
+      - py3-deprecated-warnings.json