Add tests for lister tasks
in order to be able to run unit tests using celery pytest fixtures, we use a dedicated swh_app fixture that ensure the "main" celery app is the test app (otherwise subtasks won't work).
Add tests for bitbucket tasks
Add tests for debian tasks
Add tests for gitlab tasks
Add tests for npm tasks
Add tests for pypi tasks
Migrated from D892 (view on Phabricator)