You will find them on vault.centos.org. Replace the mirrorlist commands in the CentOS-Base.repo and perhaps other files by baseurl that point to the vault, then install centos-release-openstack-newton. After that, you also need to tweak the baseurl directives in the three new repo files so that they point to the vault.

I installed the Newton version of Packstack this way. Not sure if more changes are required for a manual installation according to the tutorial.

EDIT: I just notice this question is from June. Why does it appear in my feed only now?

Running

yum install https://repos.fedorapeople.org/repos/openstack/openstack-newton/rdo-release-newton-5.noarch.rpm

should add the repository, then try: yum install centos-release-openstack-newton

The openstack-newton yum package was included in the extras repository by default, but it was taken out following newer versions of openstack. This should let you install.

Source: https: //docs.openstack.org/newton/install-guide-rdo/environment-packages.html