Refs #27025 -- Fixed "invalid escape sequence" warning in auth_tests on Python 3.6.

tests/auth_tests/urls.py

@@ -62,7 +62,7 @@ def userpage(request):
     pass
 
 
-uid_token = '(?P<uidb64>[0-9A-Za-z_\-]+)/(?P<token>[0-9A-Za-z]{1,13}-[0-9A-Za-z]{1,20})'
+uid_token = r'(?P<uidb64>[0-9A-Za-z_\-]+)/(?P<token>[0-9A-Za-z]{1,13}-[0-9A-Za-z]{1,20})'
 
 # special urls for auth test cases
 urlpatterns = auth_urlpatterns + [