--- a/mercurial/filemerge.py	Sun Oct 06 13:17:19 2019 -0400
+++ b/mercurial/filemerge.py	Sun Oct 06 13:28:56 2019 -0400
@@ -18,6 +18,7 @@
     nullid,
     short,
 )
+from .pycompat import open
 
 from . import (
     encoding,