Gatenkaas [1] filed a deletion request for archlinux-artwork [2]: I have the same problem. $ cd /var/tmp/pamac-build-[your-name]/archlinux-artwork $ updpkgsums
The result is a PKGBUILD with the old checksum:
md5sums=('ce4aefa72574465eb74e4d0a795aee5a')
That works and installs fine.
[1] https://aur.archlinux.org/account/Gatenkaas/
[2] https://aur.archlinux.org/pkgbase/archlinux-artwork/
