Horizon will not come up after restart of overcloud controllers in Red Hat OpenStack Platform 13

Issue

Horizon will not come up after restart of overcloud controllers in Red Hat OpenStack Platform 13

• run openstack overcloud deploy to push a configuration change via a stack update

• reboot controller node

Horizon will not come up and one will get an HTTP 500 error. Check error logs to confirm that there's the following permissions issue:

[root@overcloud-controller-0 ~]# grep -i permission /var/log/containers/httpd/horizon/horizon_error.log
[Wed Nov 07 23:29:41.155014 2018] [:error] [pid 57] [remote 192.168.102.7:0] ValueError: Unable to configure handler 'file': [Errno 13] Permission denied: '/var/log/horizon/horizon.log'
[Wed Nov 07 23:29:47.932982 2018] [:error] [pid 59] [remote 192.168.102.7:0] ValueError: Unable to configure handler 'file': [Errno 13] Permission denied: '/var/log/horizon/horizon.log'
[Wed Nov 07 23:29:55.489593 2018] [:error] [pid 59] [remote 192.168.102.7:156] ValueError: Unable to configure handler 'file': [Errno 13] Permission denied: '/var/log/horizon/horizon.log'
[root@overcloud-controller-0 ~]# date
Wed  7 Nov 23:32:08 UTC 2018