diff -r 021607b4ef49 -r a568a46751b6 mercurial/pycompat.py
--- a/mercurial/pycompat.py	Mon Oct 09 12:42:28 2017 -0700
+++ b/mercurial/pycompat.py	Wed Oct 11 17:27:21 2017 -0700
@@ -314,3 +314,5 @@
     stringio = cStringIO.StringIO
     maplist = map
     rawinput = raw_input
+
+isjython = sysplatform.startswith('java')