code: def _plain_auth_in_stage2(self, username, _unused, stanza):
          
          password=stanza.xpath_eval("a:query/a:password",{"a":"jabber:iq:auth"})
          if password:
              password=from_utf8(password[0].getContent())
          if not password:
              self.__logger.debug("No password found in plain auth request")
              iq=stanza.make_error_response("bad-request")
              self.send(iq)
              return
  
          if self.check_password(username,password):
              iq=stanza.make_result_response()
              self.send(iq)
              self.peer_authenticated=True
              self.auth_method_used="plain"
              self.state_change("authorized",self.peer)
              self._post_auth()
          else:
              self.__logger.debug("Plain auth failed")
              iq=stanza.make_error_response("bad-request")
              e=iq.get_error()
              e.add_custom_condition('jabber:iq:auth:error',"user-unauthorized")
              self.send(iq)
docs: Handle the second stage (<iq type='set'/>) of legacy "plain"
          authentication.
  
          [server only]