下载软件仓库失败是什么情况？

[zzhua1623]

软件更新提示错误：下载软件仓库失败。
W:The repository 'http://ppa.launchpad.net/tualatrix/ppa/ubuntu xenial Release' does not have a Release file., W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use., W:See apt-secure(8) manpage for repository creation and user configuration details., E:Failed to fetch http://ppa.launchpad.net/tualatrix/ppa/ ... 4/Packages 404 Not Found, E:Failed to fetch http://ppa.launchpad.net/tualatrix/ppa/ ... 6/Packages 404 Not Found, E:Some index files failed to download. They have been ignored, or old ones used instead。
.这是什么情况？

[poloshiao]

W:The repository 'http://ppa.launchpad.net/tualatrix/ppa/ubuntu xenial Release' does not have a Release file.,

http://ppa.launchpad.net/tualatrix/ppa/ubuntu/dists/
只有到 trusty (14.04) 沒有到 xenial (16.04)