tripleoclient fails with error message "No section: 'auth'" if it can't find undercloud-passwords.conf

Issue

"If you SSH to the undercloud as root, then forget to su - stack, this happens:

# source stackrc
# openstack overcloud deploy --templates
No section: 'auth'

Which appears to be because tripleo can't find the file with the passwords in."
source: https://bugs.launchpad.net/tripleo/+bug/1536156.

Similar if the file doesn't exist at all.