問題描述：
sudo apt-get update 報錯：
W: The repository 'http://ppa.launchpad.net/deb-rob/ros-trusty/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://ppa.launchpad.net/deb-rob/ros-trusty/ubuntu/dists/xenial/main/binary-amd64/Packages 404 Not Found [IP: 91.189.95.85 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.
解決方法：将對應的ppa删除
（1）切換到對應的ppa目錄
cd /etc/apt/sources.list.d
（2）在該目錄下ls，即可以看到對應的無法下載下傳的deb-rob-ubuntu-ros-trusty-xenial.list,删除該.list即可（安全起見，可以進行添加字尾.bak的備份）
sudo mv deb-rob-ubuntu-ros-trusty-xenial.list deb-rob-ubuntu-ros-trusty-xenial.list.bak
（3）重新更新
sudo apt-get update
參考文獻：https://www.cnblogs.com/wenzheshen/p/6599636.html