tests: Address flake8 issue

Signed-off-by: Stephen Finucane <stephen@that.guru>
(cherry picked from commit d556955)

Author: stephenfin

patchwork/tests/test_series.py

@@ -35,9 +35,9 @@ def _parse_mbox(self, name, counts, project=None):
         mbox = mailbox.mbox(os.path.join(TEST_SERIES_DIR, name), create=False)
         for msg in mbox:
             obj = parser.parse_mail(msg, project.listid)
-            if type(obj) == models.Cover:
+            if type(obj) is models.Cover:
                 results[0].append(obj)
-            elif type(obj) == models.Patch:
+            elif type(obj) is models.Patch:
                 results[1].append(obj)
             else:
                 results[2].append(obj)