diff -r f99d64e8a4e4 -r f0b6fbea00cf hgext/narrow/narrowbundle2.py
--- a/hgext/narrow/narrowbundle2.py	Thu Mar 22 21:19:31 2018 +0900
+++ b/hgext/narrow/narrowbundle2.py	Thu Mar 22 21:56:20 2018 +0900
@@ -29,6 +29,9 @@
     util,
     wireproto,
 )
+from mercurial.utils import (
+    stringutil,
+)
 
 NARROWCAP = 'narrow'
 _NARROWACL_SECTION = 'narrowhgacl'
@@ -449,7 +452,7 @@
         except OSError as e:
             if e.errno != errno.ENOENT:
                 ui.warn(_('error removing %s: %s\n') %
-                        (undovfs.join(undofile), util.forcebytestr(e)))
+                        (undovfs.join(undofile), stringutil.forcebytestr(e)))
 
     # Remove partial backup only if there were no exceptions
     vfs.unlink(chgrpfile)