error: allow a 'hint' to OutOfBandError

This will be useful when changing the behavior of OutOfBandError for ssh in the
next changeset.

mercurial/dispatch.py

@@ -193,8 +193,15 b' def _runcatch(req):'
             ui.warn(_("hg: %s\n") % inst.args[1])
             commands.help_(ui, 'shortlist')
     except error.OutOfBandError, inst:
-        ui.warn(_("abort: remote error:\n"))
-        ui.warn(''.join(inst.args))
+        if inst.args:
+            msg = _("abort: remote error:\n")
+        else:
+            msg = _("abort: remote error\n")
+        ui.warn(msg)
+        if inst.args:
+            ui.warn(''.join(inst.args))
+        if inst.hint:
+            ui.warn('(%s)\n' % inst.hint)
     except error.RepoError, inst:
         ui.warn(_("abort: %s!\n") % inst)
         if inst.hint:

mercurial/error.py

@@ -64,6 +64,10 b' class ConfigError(Abort):'
 class OutOfBandError(Exception):
     """Exception raised when a remote repo reports failure"""
 
+    def __init__(self, *args, **kw):
+        Exception.__init__(self, *args)
+        self.hint = kw.get('hint')
+
 class ParseError(Exception):
     """Raised when parsing config files and {rev,file}sets (msg[, pos])"""