When I look at /usr/libexec/openstack-tripleo/install-dependencies, I find it does call for EPEL:

if [ "$TRIPLEO_OS_FAMILY" = "redhat" ]; then
    # For CentOS, python-pip and jq are in EPEL
    if [ "$TRIPLEO_OS_DISTRO" = "centos" ] && [ ! -f /etc/yum.repos.d/epel.repo ]; then
        echo EPEL repository is required to install python-pip for CentOS.
        echo See http://fedoraproject.org/wiki/EPEL
        exit 1
    fi
    sudo -E yum install -y python-lxml libvirt-python libvirt qemu-img qemu-kvm git python-pip openssl-devel python-devel gcc audit python-virtualenv openvswitch python-yaml net-tools redhat-lsb-core libxslt-devel jq openssh-server libffi-devel which glusterfs-api python-netaddr

    sudo service libvirtd restart
    sudo service openvswitch restart
    sudo chkconfig openvswitch on
fi