Erreur : Pas de version xéniale pour kernel-ppa

Erreur complète :

Err:11 http://ppa.launchpad.net/kernel-ppa/ppa/ubuntu xenial Release
  404  Not Found
Reading package lists... Done                      
E: The repository 'http://ppa.launchpad.net/kernel-ppa/ppa/ubuntu xenial 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.

Normal sources.list :

$ cat /etc/apt/sources.list
deb http://ports.ubuntu.com/ xenial main restricted universe multiverse
deb-src http://ports.ubuntu.com/ xenial main restricted universe multiverse

deb http://ports.ubuntu.com/ xenial-updates main restricted universe multiverse
deb-src http://ports.ubuntu.com/ xenial-updates main restricted universe multiverse

deb http://ports.ubuntu.com/ xenial-security main restricted universe multiverse
deb-src http://ports.ubuntu.com/ xenial-security main restricted universe multiverse

deb http://ports.ubuntu.com/ xenial-backports main restricted universe multiverse
deb-src http://ports.ubuntu.com/ xenial-backports main restricted universe multiverse

Je vois que le kernel-ppa a pas de dossier xenial dist . Comment puis-je corriger cette erreur ou désactiver l'erreur due à l'absence de dossier xenial ?