Disable check package sign
$ vim /etc/pacman.conf
...
#SigLevel = Required DatabaseOptional
SigLevel = Never
...
Or import key
$ sudo pacman-key --init
$ sudo pacman-key -r 7F2D434B9741E8AC
https://wiki.archlinux.org/index.php/Pacman/Package_signing
使用 yaourt 安装软件提醒“所需的密钥从密钥环中丢失”
原文：https://www.cnblogs.com/yanghao2008/p/14965579.html