--- a/mercurial/posix.py	Sat Apr 07 20:50:38 2018 +0900
+++ b/mercurial/posix.py	Sat Apr 07 21:09:21 2018 +0900
@@ -469,9 +469,6 @@
 def quotecommand(cmd):
     return cmd
 
-def popen(command, mode='r'):
-    return os.popen(command, mode)
-
 def testpid(pid):
     '''return False if pid dead, True if running or not sure'''
     if pycompat.sysplatform == 'OpenVMS':