OpenShift installation fails at TASK [Run variable sanity checks] while running prerequisites.yml playbook.

Issue

• OpenShift installation fails at TASK [Run variable sanity checks] while running prerequisites.yml playbook.

TASK [Run variable sanity checks] **************************************************************************************
task path: /usr/share/ansible/openshift-ansible/playbooks/init/sanity_checks.yml:14
fatal: [master.example.com]: FAILED! => {
    "msg": "last_checked_host: master.example.com, last_checked_var: ansible_python;'NoneType' object has no attribute '__getitem__'"
}
        to retry, use: --limit @/usr/share/ansible/openshift-ansible/playbooks/prerequisites.retry