When doing a yum update I get

Error: Package: etckeeper-1.18.7-2.el6.noarch (epel) Requires: hostname

Problem is currently fixed in epel-testing re https://bugzilla.redhat.com/show_bug.cgi?id=1577707

So to fix you just need to install it from testing:

sudo yum install --enablerepo=epel-testing etckeeper