我尝试过「已解决」GPGME密钥和PGP签名问题 / 新手园地 / Arch Linux 中文论坛 -U 的方式覆盖原来的gpg，现在安装一个包或者更新似乎都是正常使用的，只是更新后依然报错
sudo pacman -Syu
:: Synchronizing package databases...
core is up to date
extra is up to date
multilib is up to date
error: failed retrieving file 'core.db' from sg.mirrors.cicku.me : SSL certificate problem: unable to get local issuer certificate
error: failed retrieving file 'extra.db' from sg.mirrors.cicku.me : SSL certificate problem: unable to get local issuer certificate
error: failed retrieving file 'multilib.db' from sg.mirrors.cicku.me : SSL certificate problem: unable to get local issuer certificate
warning: too many errors from sg.mirrors.cicku.me, skipping for the remainder of this transaction
:: Starting full system upgrade...
there is nothing to do