code: @Override
      public void sendAppException(Throwable throwable) {
          checkState();
          SofaResponse response = new SofaResponse();
          response.setAppResponse(throwable);
          sendSofaResponse(response, null);
      }
docs: A->B(当前)->C的场景下，将远程服务端C的业务异常异步返回给调用者A
  
  @see SofaResponseCallback#onAppException(Throwable, String, RequestBase)