Fix encoding of namespace uris.

Namespace for openid is usually unicode type, but it is not encoded to string in response.

openid/message.py

@@ -273,7 +273,7 @@ def toPostArgs(self):
                 ns_key = 'openid.ns'
             else:
                 ns_key = 'openid.ns.' + alias
-            args[ns_key] = ns_uri
+            args[ns_key] = oidutil.toUnicode(ns_uri).encode('UTF-8')
 
         for (ns_uri, ns_key), value in self.args.iteritems():
             key = self.getKey(ns_uri, ns_key)