diff -r 8e0327dae3f4 -r a9c71d578a1c mercurial/debugcommands.py
--- a/mercurial/debugcommands.py	Fri Aug 12 11:30:17 2016 +0900
+++ b/mercurial/debugcommands.py	Fri Aug 12 11:35:17 2016 +0900
@@ -1029,6 +1029,8 @@
                 base85,
                 bdiff,
                 mpatch,
+            )
+            from .cext import (
                 osutil,
             )
             dir(bdiff), dir(mpatch), dir(base85), dir(osutil) # quiet pyflakes