笔者当前系统ubuntu18.04，使用apt-get update 出现错误如下
Hit:1 http://mirrors.aliyun.com/ubuntu bionic InRelease
Hit:2 http://mirrors.aliyun.com/ubuntu bionic-security InRelease
Hit:3 http://mirrors.aliyun.com/ubuntu bionic-updates InRelease
Hit:4 http://mirrors.aliyun.com/ubuntu bionic-proposed InRelease
Hit:5 http://mirrors.aliyun.com/ubuntu bionic-backports InRelease
Hit:6 http://ppa.launchpad.net/deadsnakes/ppa/ubuntu bionic InRelease
Hit:7 http://ppa.launchpad.net/graphics-drivers/ppa/ubuntu bionic InRelease
Hit:8 http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu bionic InRelease
Ign:9 http://ppa.launchpad.net/webupd8team/sublime-text-3/ubuntu bionic InRelease
Err:10 http://ppa.launchpad.net/webupd8team/sublime-text-3/ubuntu bionic Release
  404  Not Found [IP: 91.189.95.83 80]
Reading package lists... Done
E: The repository 'http://ppa.launchpad.net/webupd8team/sublime-text-3/ubuntu bionic Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

同学们在目录 /etc/apt/sources.list.下  ls可以看到相关文件如下(大同小异）：
 webupd8team-ubuntu-sublime-text-3-bionic.list       upd8team-ubuntu-sublime-text-3-bionic.list.save

将这两个文件rm，再使用如下命令即可更新：
sudo apt-get update