Description of problem: Fedora 22 is planning to switch over to dnf from yum as per https://fedoraproject.org/wiki/Changes/ReplaceYumWithDNF Please switch from yum/yum-utils to dnf/dnf-plugins-core. Thanks!
Plague Builder does not use Yum directly but Mock (which may or may not use Yum as package tool). http://pkgs.fedoraproject.org/cgit/plague.git/commit/?id=fdf64cf8f71728912168dbfd04a42b98d2c983d9