code: private Observable<ChatResult> handleMessageError(MessageProcessor mp, Throwable t) {
          return persistenceController.updateStoreForSentError(mp.getConversationId(), mp.getTempId(), mp.getSender())
                  .map(success -> new ChatResult(false, new ChatResult.Error(0, t)));
      }
docs: Handle failure when sent message.
  
  @param mp Message processor holding message sent details.
  @param t  Thrown exception.
  @return Observable with Chat SDK result.