I wanted to make a byte-sized contribution but there were no Jira tickets so we decided, thanks to a conversation with @jmbowman through the Open Edx Community #incr (Slack) channel, to collaborate in the elimination of warnings listed in the Warnings Report at https://build.testeng.edx.org/job/edx-platform-python-pipeline-master/warning_5freport_5fall_2ehtml/ This PR contributes to the elimination of deprecation warnings, specifically the one mentioned above and reported in the Warnings Report. Changed assertNotRegexpMatches to assertNotRegex in the following files: cms/djangoapps/contentstore/views/tests/test_preview.py cms/djangoapps/contentstore/views/tests/test_item.py lms/djangoapps/commerce/tests/test_views.py lms/djangoapps/dashboard/tests/test_sysadmin.py This warning occurs due to deprecation in python 3.5: https://docs.python.org/3.5/library/unittest.html#unittest.TestCase.assertNotRegex