我一直在尝试升级到 Ubuntu 18.04，但是当我尝试
do-release-upgrade -c
我得到这个输出
Checking for a new Ubuntu release
No new release found.
我已经检查了发布日期是 4 月 26 日，但仍然没有收到任何更新......
我对 Linux 有点陌生，所以如果我在任何方面弄错了，请原谅我。
当我运行时sudo apt-get update，我收到此错误消息：
W: The repository 'http://ppa.launchpad.net/ubuntu-wine/ppa/ubuntu yakkety Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://ppa.launchpad.net/ubuntu-wine/ppa/ubuntu/dists/yakkety/main/binary-amd64/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
由于此错误，我无法安装任何应用程序，请详细帮助我，我对 Linux 非常陌生。