PGP wrong in archlinux

what is the issue

I try to install sublime in archlinux by the follow command, the software will be downloaded from the archlinuxcn repository.

sudo pacman -S archlinuxcn/sublime-text

wrong appears as follow.

error: sublime-text: signature from "SY Zhang <lastavengers@outlook.com>" is unknown trust
:: File /var/cache/pacman/pkg/sublime-text-2.0.2-4-x86_64.pkg.tar.xz is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n] 
error: failed to commit transaction (invalid or corrupted package (PGP signature))
Errors occurred, no packages were upgraded.

---

solve

step 1

I don’t know why it works, but it makes me install sublime-text successfully. I modified the file /etc/pacman.conf, changed

[archlinuxcn]
SigLevel = Optional TrustedOnly
Server = http://mirrors.163.com/archlinux-cn/$arch

to

[archlinuxcn]
SigLevel = Never # Optional TrustedOnly
Server = http://mirrors.163.com/archlinux-cn/$arch

step 2

sudo pacman -Syy

step 3

go ahead to install sublime-text.

sudo pacman -S sublime-text