--- a/hgext/extdiff.py	Sun Nov 10 07:30:14 2019 -0800
+++ b/hgext/extdiff.py	Fri Nov 08 11:19:20 2019 -0800
@@ -655,7 +655,7 @@
         # in an unknown encoding anyway), but avoid double separators on
         # Windows
         docpath = stringutil.escapestr(path).replace(b'\\\\', b'\\')
-        self.__doc__ %= {r'path': pycompat.sysstr(stringutil.uirepr(docpath))}
+        self.__doc__ %= {'path': pycompat.sysstr(stringutil.uirepr(docpath))}
         self._cmdline = cmdline
         self._isgui = isgui