执行sudo apt-get update报错：
E: Failed to fetch http://ppa.launchpad.net/v-launchpad-jochen-sprickerhof-de/pcl/ubuntu/dists/xenial/main/binary-amd64/Packages 404 Not Found [IP: 91.189.95.83 80] E: Some index files failed to download. They have been ignored, or old ones used instead.
解决方法：删除对应的ppa即可。
1.切换到对应ppa目录下
cd /etc/apt/sources.list.d
2.查看相关ppa文件
ll
3.删除无法下载的文件
sudo rm v-launchpad-jochen-sprickerhof-de-ubuntu-pcl-xenial.list
4.重新执行跟新命令
sudo apt-get update
参考链接：https://blog.csdn.net/u014775723/article/details/85224026
