wireproto: add out-of-band error class to allow remote repo to report errors Older clients will still print the provided error message and not much else: over ssh, this will be each line prefixed with 'remote: ' in addition to an "abort: unexpected response: '\n'"; over http, this will be the '---%<---' banners in addition to the 'does not appear to be a repository' message. Currently, clients with this patch will display 'abort: remote error:\n' and the provided error text, but it is trivial to style the error text however is deemed appropriate.

--- a/mercurial/error.py	Wed Aug 03 16:41:14 2011 -0500
+++ b/mercurial/error.py	Tue Aug 02 15:21:10 2011 -0400
@@ -39,6 +39,9 @@
 class ConfigError(Abort):
     'Exception raised when parsing config files'
 
+class OutOfBandError(Exception):
+    'Exception raised when a remote repo reports failure'
+
 class ParseError(Exception):
     'Exception raised when parsing config files (msg[, pos])'