--- a/mercurial/error.py	Fri Apr 03 12:37:44 2009 -0500
+++ b/mercurial/error.py	Fri Apr 03 13:20:52 2009 -0500
@@ -62,3 +62,6 @@
 
 class SignatureError(Exception):
     pass
+
+class Abort(Exception):
+    """Raised if a command needs to print an error and exit."""