MarsSeed [1] filed a deletion request for sem [2]: EOL alpha software from 2006.
PKGBUILD likely broken since 2012-2013:
==> ERROR: sem is not available for the 'x86_64' architecture.
==> ERROR: license should be an array
==> ERROR: source should be an array
==> ERROR: url should not be an array
[1] https://aur.archlinux.org/account/MarsSeed/
[2] https://aur.archlinux.org/pkgbase/sem/
