Pacman

error: key "xxxxx" could not be looked up remotely

Problem

When upgrading with pacman the following error occurs

....
downloading required keys...
error: key "xxxxx" could not be looked up remotely
error: required key missing from keyring
error: failed to commit transaction (unexpected error)
Errors occurred, no packages were upgraded.

Solution

Upgrade archlinux-keyring before upgrading the system

sudo pacman -S archlinux-keyring

Reference: https://bbs.archlinux.org/viewtopic.php?id=193382