The koji in EPEL-7 works just fine
As of yesterday,
installing koji-builder fails with error:
Error: Package: koji-builder-1.10.1-8.el7.noarch (epel)
Requires: python2-multilib
You could try using --skip-broken to work around the problem
You could try running: rpm -Va --nofiles --nodigest
CentOS 7.2