Openstack deploy fails with TypeError: 'NoneType' object is not subscriptable

Issue

• When running the openstack overcloud deploy step, instead of producing errors that are meaningful to the user with Template issues, Python just produces stack traces.

2021-05-04 16:14:49,131 INFO     START with options: overcloud deploy --stack psi-c0-osp16-test --timeout 100 --deployed-server --disable-validations --overcloud-ssh-user stack --overcloud-ssh-key ~/.ssh/id_rsa --verbose --answers-file answers.yaml -n network_data.yaml -r roles_data.yaml --stack-only
2021-05-04 16:14:49,131 INFO     command: overcloud deploy -> tripleoclient.v1.overcloud_deploy.DeployOvercloud (auth=True)
2021-05-04 16:14:49,131 INFO     Using auth plugin: password
2021-05-04 16:14:49,132 INFO     Exception occured while running the command
2021-05-04 16:14:49,132 INFO       File "/usr/lib/python3.6/site-packages/tripleoclient/command.py", line 32, in run
2021-05-04 16:14:49,133 INFO         super(Command, self).run(parsed_args)
2021-05-04 16:14:49,133 INFO       File "/usr/lib/python3.6/site-packages/osc_lib/command/command.py", line 41, in run
2021-05-04 16:14:49,133 INFO         return super(Command, self).run(parsed_args)
2021-05-04 16:14:49,133 INFO       File "/usr/lib/python3.6/site-packages/cliff/command.py", line 185, in run
2021-05-04 16:14:49,133 INFO         return_code = self.take_action(parsed_args) or 0
2021-05-04 16:14:49,133 INFO       File "/usr/lib/python3.6/site-packages/tripleoclient/v1/overcloud_deploy.py", line 1022, in take_action
2021-05-04 16:14:49,133 INFO         self._update_parameters(parsed_args, stack)
2021-05-04 16:14:49,133 INFO       File "/usr/lib/python3.6/site-packages/tripleoclient/v1/overcloud_deploy.py", line 123, in _update_parameters
2021-05-04 16:14:49,133 INFO         if nbd_tls_key in roledata[key]['config_settings']:
2021-05-04 16:14:49,133 INFO     TypeError: 'NoneType' object is not subscriptable
2021-05-04 16:14:49,134 INFO     'NoneType' object is not subscriptable
2021-05-04 16:14:49,134 INFO     END return value: 1