When installing epel repository in centos in some conditions there is an error during yum update.
This is an epel repository bug
https://bugs.centos.org/view.php?id=12597
Solution
Work around applied:
In /etc/yum.repos.d/epel.repo, commented out the following lines;
#mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-7&arch=$basearch
Enabled baseurl lines in configuration file and repointed to new repo.
baseurl=http://mirror.xnet.co.nz/pub/epel/7/$basearch
Yum update found that epel-release was out of date and updated to epel-release 7-11. Working as expected.