tests: Set maxDiff to None unconditionally.

analytics/tests/test_views.py

@@ -32,8 +32,6 @@ class TestStatsEndpoint(ZulipTestCase):
         self.assert_in_response("Zulip Analytics for", result)
 
 class TestGetChartData(ZulipTestCase):
-    maxDiff = None  # type: int
-
     def setUp(self):
         # type: () -> None
         self.realm = get_realm('zulip')

zerver/lib/test_classes.py

@@ -84,6 +84,9 @@ class UploadSerializeMixin(SerializeMixin):
         super(UploadSerializeMixin, cls).setUpClass(*args, **kwargs)
 
 class ZulipTestCase(TestCase):
+    # Ensure that the test system just shows us diffs
+    maxDiff = None  # type: int
+
     '''
     WRAPPER_COMMENT: