diff --git a/swh/lister/debian/tests/test_tasks.py b/swh/lister/debian/tests/test_tasks.py
index bd1d0b4..a5a5d0e 100644
--- a/swh/lister/debian/tests/test_tasks.py
+++ b/swh/lister/debian/tests/test_tasks.py
@@ -1,29 +1,26 @@
-from time import sleep
-from celery.result import GroupResult
-
 from unittest.mock import patch
 
 
 def test_ping(swh_app, celery_session_worker):
     res = swh_app.send_task(
         'swh.lister.debian.tasks.ping')
     assert res
     res.wait()
     assert res.successful()
     assert res.result == 'OK'
 
 
 @patch('swh.lister.debian.tasks.DebianLister')
 def test_lister(lister, swh_app, celery_session_worker):
     # setup the mocked DebianLister
     lister.return_value = lister
     lister.run.return_value = None
 
     res = swh_app.send_task(
         'swh.lister.debian.tasks.DebianListerTask', ('stretch',))
     assert res
     res.wait()
     assert res.successful()
 
     lister.assert_called_once_with()
     lister.run.assert_called_once_with('stretch')