Hello,
I tried to install katello client on CentOS 6, following the documentation [1], but the install fail because katello-client-repos-latest.rpm (and all others katello-*.rpm) are missing in EL6 client repo [2] compared to EL7 client repo [3].
[1] Foreman :: Plugin Manuals
[2] https://fedorapeople.org/groups/katello/releases/yum/3.6/client/el6/x86_64/
[3] https://fedorapeople.org/groups/katello/releases/yum/3.6/client/el7/x86_64/