answer_unsupported (OpenID::Server::AssociateRequest)

    # File lib/openid/server.rb, line 377
          def answer_unsupported(message, preferred_association_type=nil,
                                 preferred_session_type=nil)
            if @message.is_openid1()
              raise ProtocolError.new(@message)
            end

            response = OpenIDResponse.new(self)
            response.fields.set_arg(OPENID_NS, 'error_code', 'unsupported-type')
            response.fields.set_arg(OPENID_NS, 'error', message)

            if preferred_association_type
              response.fields.set_arg(
                  OPENID_NS, 'assoc_type', preferred_association_type)
            end

            if preferred_session_type
              response.fields.set_arg(
                  OPENID_NS, 'session_type', preferred_session_type)
            end

            return response
          end