diff -r 020a896a5292 -r e62a456b8dc5 mercurial/error.py
--- a/mercurial/error.py	Mon Jan 12 13:35:35 2009 -0600
+++ b/mercurial/error.py	Mon Jan 12 13:51:43 2009 -0600
@@ -59,3 +59,6 @@
 # derived from KeyboardInterrupt to simplify some breakout code
 class SignalInterrupt(KeyboardInterrupt):
     """Exception raised on SIGTERM and SIGHUP."""
+
+class SignatureError(Exception):
+    pass