diff -r f42dec9c976e -r c0a6c19690ff mercurial/pycompat.py
--- a/mercurial/pycompat.py	Wed Oct 11 21:24:32 2017 -0700
+++ b/mercurial/pycompat.py	Thu Oct 12 19:20:04 2017 -0700
@@ -316,3 +316,7 @@
     rawinput = raw_input
 
 isjython = sysplatform.startswith('java')
+
+isdarwin = sysplatform == 'darwin'
+isposix = osname == 'posix'
+iswindows = osname == 'nt'