mercurial/commands.py

--- a/mercurial/commands.py	Wed May 03 15:25:06 2017 +0530
+++ b/mercurial/commands.py	Fri Apr 28 00:49:30 2017 +0530
@@ -2759,7 +2759,7 @@
     Returns 0 if successful.
     """
 
-    keep = opts.get('system') or []
+    keep = opts.get(r'system') or []
     if len(keep) == 0:
         if pycompat.sysplatform.startswith('win'):
             keep.append('windows')