Ubuntu18.04安装everpad报错

Question

问题描述

想要在Ubuntu18.04使用印象笔记，安装linux下的客户端everpad
通过ppa方式：
sudo add-apt-repository ppa:nvbn-rm/ppa
sudo apt-get update

问题出现的平台版本及自己尝试过哪些方法

在执行sudo add-apt-repository ppa:nvbn-rm/ppa的时候提示没有一个发布的文件

相关代码

Hit:1 http://archive.ubuntukylin.com:10006/ubuntukylin xenial InRelease
Ign:2 http://dl.google.com/linux/ch... stable InRelease
Hit:3 http://dl.google.com/linux/ch... stable Release
Get:5 http://security.ubuntu.com/ub... bionic-security InRelease [83.2 kB]
Hit:6 http://cn.archive.ubuntu.com/... bionic InRelease
Ign:7 http://ppa.launchpad.net/nvbn... bionic InRelease
Get:8 http://cn.archive.ubuntu.com/... bionic-updates InRelease [88.7 kB]
Err:9 http://ppa.launchpad.net/nvbn... bionic Release
404 Not Found [IP: 91.189.95.83 80]
Hit:10 http://cn.archive.ubuntu.com/... bionic-backports InRelease
Reading package lists... Done
E: The repository 'http://ppa.launchpad.net/nvbn-rm/ppa/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.

你期待的结果是什么？实际看到的错误信息又是什么？