Wait for text to appear

Adding a wait statement to allow ajax calls to finish before making assertions
about text that has changed. Fixes TNL-3943 flaky test ticket.

common/test/acceptance/pages/lms/discussion.py

@@ -277,6 +277,7 @@ class DiscussionThreadPage(PageObject, DiscussionPageMixin):
     def submit_comment_edit(self, comment_id, new_comment_body):
         """Click the submit button on the comment editor"""
         self._find_within("#comment_{} .post-update".format(comment_id)).first.click()
+        self.wait_for_ajax()
         EmptyPromise(
             lambda: (
                 not self.is_comment_editor_visible(comment_id) and

common/test/acceptance/tests/discussion/test_discussion.py

@@ -547,7 +547,6 @@ class DiscussionCommentEditTest(BaseDiscussionTestCase):
         self.assertFalse(page.is_comment_editable("comment_other_author"))
         self.edit_comment(page, "comment_self_author")
 
-    @skip  # TODO: See TNL-3943
     def test_edit_comment_as_moderator(self):
         self.setup_user(roles=["Moderator"])
         self.setup_view()