--- a/mercurial/pure/osutil.py	Thu Oct 12 19:20:04 2017 -0700
+++ b/mercurial/pure/osutil.py	Thu Oct 12 23:30:46 2017 -0700
@@ -64,7 +64,7 @@
             result.append((fn, _mode_to_kind(st.st_mode)))
     return result
 
-if pycompat.osname != 'nt':
+if not pycompat.iswindows:
     posixfile = open
 
     _SCM_RIGHTS = 0x01