Use setUpTestData() to speed up tests

Pylint's `bad-classmethod-argument` is disabled for each definition
to avoid rewriting the method bodies just to rename `self` → `cls`.
This can be done gradually, as the setUpTestData methods are modified
along the way.

bookwyrm/tests/models/test_site.py

@@ -12,7 +12,8 @@ from bookwyrm import models, settings
 class SiteModels(TestCase):
     """tests for site models"""
 
-    def setUp(self):
+    @classmethod
+    def setUpTestData(self):  # pylint: disable=bad-classmethod-argument
         """we need basic test data and mocks"""
         with patch("bookwyrm.suggested_users.rerank_suggestions_task.delay"), patch(
             "bookwyrm.activitystreams.populate_stream_task.delay"