--- a/mercurial/pycompat.py	Wed Aug 02 22:58:38 2017 +0900
+++ b/mercurial/pycompat.py	Wed Aug 02 22:51:19 2017 +0900
@@ -16,6 +16,7 @@
 import sys
 
 ispy3 = (sys.version_info[0] >= 3)
+ispypy = (r'__pypy__' in sys.builtin_module_names)
 
 if not ispy3:
     import cookielib