don't depend on features of Exception as much

BaseException.message has been deprecated, so we try to not rely on it.

mercurial/hgweb/common.py

@@ -73,10 +73,12 b' class ErrorResponse(Exception):'
     def __init__(self, code, message=None, headers=[]):
         if message is None:
             message = _statusmessage(code)
-        Exception.__init__(self, code, message)
+        super(Exception, self).__init__()
         self.code = code
         self.message = message
         self.headers = headers
+    def __str__(self):
+        return self.message
 
 class continuereader(object):
     def __init__(self, f, write):