我使用 Software Sources 程序添加了一些额外的存储库。但是当我重新加载包数据库时，出现如下错误：
W：GPG 错误：http : //ppa.launchpad.net trusty InRelease：以下签名无法验证，因为公钥不可用：NO_PUBKEY 8BAF9A6F
apt-key根据官方的 Ubuntu 文档，我知道我可以在终端中修复它。但我希望以图形方式进行。有没有办法在不使用终端的情况下做到这一点？
每当我尝试更新终端时都会告诉我这个
Ign:20 http://download.opensuse.org/repositories/home:/strycore/xUbuntu_16.04 ./ Release.gpg
Reading package lists... Done
W: GPG error: http://download.opensuse.org/repositories/home:/strycore/xUbuntu_16.04 ./ Release: The following signatures were invalid: EXPKEYSIG 2F7F0DA5FD5B64B9 home:strycore OBS Project <home:strycore@build.opensuse.org>
E: The repository 'http://download.opensuse.org/repositories/home:/strycore/xUbuntu_16.04 ./ Release' is not signed.
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.
'http://download.opensuse.org/repositories/home:/strycore/xUbuntu_16.04 ./ Release' 未签名的答案并不能解决我的问题。