sevi@pandabook:~$ sudo apt update
[sudo] password for sevi:
.
.
404 Not Found [IP: 91.189.95.83 80]
Reading package lists… Done
E: The repository ‘http://ppa.launchpad.net/ubuntubudgie/backports/ubuntu disco 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.