Comment 5 for bug 1730314

Folks who are experiencing this in CentOS7: CentOS 7.5 has recently been released, which bumps the libvirt version to 3.9.0; libvirt-python must match libvirt's version, so capping it at anything lower than 3.9.0 will not work. For now, it's necessary to modify the advice above - in /etc/openstack_deploy/user_variables.yml:

repo_build_upper_constraints_overrides:
  - "libvirt-python==3.9.0"

I think OSA should either pin the libvirt package to a version that fits the OS tested requirements, or else remove the the libvirt-python upper constraint to overcome this issue.