diff -r fbce78c58f1e -r 3f8f53190d6a mercurial/util.py
--- a/mercurial/util.py	Sun Feb 19 01:00:10 2017 +0900
+++ b/mercurial/util.py	Sun Feb 19 01:16:45 2017 +0900
@@ -1009,20 +1009,16 @@
     env['HG'] = hgexecutable()
     return env
 
-def system(cmd, environ=None, cwd=None, onerr=None, errprefix=None, out=None):
+def system(cmd, environ=None, cwd=None, out=None):
     '''enhanced shell command execution.
     run with environment maybe modified, maybe in different dir.
 
-    if command fails and onerr is None, return status, else raise onerr
-    object as exception.
-
     if out is specified, it is assumed to be a file-like object that has a
     write() method. stdout and stderr will be redirected to out.'''
     try:
         stdout.flush()
     except Exception:
         pass
-    origcmd = cmd
     cmd = quotecommand(cmd)
     if pycompat.sysplatform == 'plan9' and (sys.version_info[0] == 2
                                     and sys.version_info[1] < 7):
@@ -1046,12 +1042,6 @@
             rc = proc.returncode
         if pycompat.sysplatform == 'OpenVMS' and rc & 1:
             rc = 0
-    if rc and onerr:
-        errmsg = '%s %s' % (os.path.basename(origcmd.split(None, 1)[0]),
-                            explainexit(rc)[0])
-        if errprefix:
-            errmsg = '%s: %s' % (errprefix, errmsg)
-        raise onerr(errmsg)
     return rc
 
 def checksignature(func):