empty vars files cause openstack-ansible to fail to combine variables

[Matthew Thode]

I'm not sure if this is an ansible problem or one in OSA (how we combine vars files), but I'll report it here.

The file itself looks like this, if you add a defunct variable (not used for anything) it works fine.

---
# licence header
# goes here

and causes this specific error

    openstack-ansible --forks 4 haproxy-install.yml
    Variable files: "-e @/etc/openstack_deploy/user_conf_files.yml -e @/etc/openstack_deploy/user_extras_variables.yml -e @/etc/openstack_deploy/user_osa_aio_variables.yml -e @/etc/openstack_deploy/user_osa_secrets_defaults.yml -e @/etc/openstack_deploy/user_osa_secrets_overrides.yml -e @/etc/openstack_deploy/user_osa_variables_defaults.yml -e @/etc/openstack_deploy/user_osa_variables_overrides.yml -e @/etc/openstack_deploy/user_rpco_secrets_defaults.yml -e @/etc/openstack_deploy/user_rpco_secrets_overrides.yml -e @/etc/openstack_deploy/user_rpco_variables_defaults.yml -e @/etc/openstack_deploy/user_rpco_variables_overrides.yml "
    ERROR: failed to combine variables, expected dicts but got a 'dict' and a 'NoneType'

[Matthew Thode (prometheanfire)]

The reason we wish to have an empty vars file is to ship it to our end users so they override the vars that we ship. They can't edit the files we ship directly because we may overwrite them (causing them to loose their overrides).

[Jean-Philippe Evrard (jean-philippe-evrard)]

That's ansible default behavior.

We could maybe check in the dynamic inventory before including as a workaround, but this is not the way we are working now.

[Jean-Philippe Evrard (jean-philippe-evrard)]

For context, conversation here:
http://eavesdrop.openstack.org/irclogs/%23openstack-ansible/%23openstack-ansible.2016-07-05.log.html#t2016-07-05T16:08:28