diff -r 829088e87032 -r c95b2f40db7c mercurial/testing/storage.py
--- a/mercurial/testing/storage.py	Sun Oct 06 14:58:41 2019 -0400
+++ b/mercurial/testing/storage.py	Sun Oct 06 17:45:05 2019 -0400
@@ -24,7 +24,7 @@
 
 
 class basetestcase(unittest.TestCase):
-    if not getattr(unittest.TestCase, r'assertRaisesRegex', False):
+    if not getattr(unittest.TestCase, 'assertRaisesRegex', False):
         assertRaisesRegex = (  # camelcase-required
             unittest.TestCase.assertRaisesRegexp
         )