diff -r 38a3767975a7 -r 0646608368a9 mercurial/extensions.py
--- a/mercurial/extensions.py	Tue Jul 25 22:49:43 2017 -0400
+++ b/mercurial/extensions.py	Fri Aug 11 15:09:54 2017 -0400
@@ -396,8 +396,8 @@
             break
 
     if currcls is object:
-        raise AttributeError(
-            _("type '%s' has no property '%s'") % (cls, propname))
+        raise AttributeError(r"type '%s' has no property '%s'" % (
+            cls, propname))
 
 def wrapfunction(container, funcname, wrapper):
     '''Wrap the function named funcname in container