ubuntu升级失败报错

执行
sudo update
sudo upgrade
后

执行sudo do-release-upgrade 提示：
Please install all available updates for your release before upgrading
有更新没升级

参考
https://zhuanlan.zhihu.com/p/20283573000

打印出来是code没升级

参考https://blog.csdn.net/jakekiller00/article/details/147016548