Getting below traceback

019-06-13 05:18:36.253 66638 DEBUG config_tempest.constants [-] Setting [service_available] octavia = False set /usr/lib/python2.7/site-packages/config_tempest/tempest_conf.py:107
 2019-06-13 05:18:36.253 66638 DEBUG config_tempest.constants [-] Setting [heat_plugin] username = admin set /usr/lib/python2.7/site-packages/config_tempest/tempest_conf.py:107
 2019-06-13 05:18:36.253 66638 DEBUG config_tempest.constants [-] Setting [heat_plugin] password = V8OfgLkaOqqMDXi0It5xi9yjK set /usr/lib/python2.7/site-packages/config_tempest/tempest_conf.py:107
 2019-06-13 05:18:36.253 66638 DEBUG config_tempest.constants [-] Setting [heat_plugin] admin_username = admin set /usr/lib/python2.7/site-packages/config_tempest/tempest_conf.py:107
 2019-06-13 05:18:36.253 66638 DEBUG config_tempest.constants [-] Setting [heat_plugin] admin_password = V8OfgLkaOqqMDXi0It5xi9yjK set /usr/lib/python2.7/site-packages/config_tempest/tempest_conf.py:107
 2019-06-13 05:18:36.253 66638 DEBUG config_tempest.constants [-] Setting [heat_plugin] project_name = demo set /usr/lib/python2.7/site-packages/config_tempest/tempest_conf.py:107
 2019-06-13 05:18:36.253 66638 CRITICAL tempest [-] Unhandled error: NoOptionError: No option 'region' in section: 'identity'
 2019-06-13 05:18:36.253 66638 ERROR tempest Traceback (most recent call last):
 2019-06-13 05:18:36.253 66638 ERROR tempest File "/bin/discover-tempest-config", line 10, in <module>
 2019-06-13 05:18:36.253 66638 ERROR tempest sys.exit(main())
 2019-06-13 05:18:36.253 66638 ERROR tempest File "/usr/lib/python2.7/site-packages/config_tempest/main.py", line 597, in main
 2019-06-13 05:18:36.253 66638 ERROR tempest verbose=args.verbose
 2019-06-13 05:18:36.253 66638 ERROR tempest File "/usr/lib/python2.7/site-packages/config_tempest/main.py", line 519, in config_tempest
 2019-06-13 05:18:36.253 66638 ERROR tempest services = Services(clients, conf, credentials)
 2019-06-13 05:18:36.253 66638 ERROR tempest File "/usr/lib/python2.7/site-packages/config_tempest/services/services.py", line 42, in __init__
 2019-06-13 05:18:36.253 66638 ERROR tempest self.discover()
 2019-06-13 05:18:36.253 66638 ERROR tempest File "/usr/lib/python2.7/site-packages/config_tempest/services/services.py", line 111, in discover
 2019-06-13 05:18:36.253 66638 ERROR tempest service.set_default_tempest_options(self._conf)
 2019-06-13 05:18:36.253 66638 ERROR tempest File "/usr/lib/python2.7/site-packages/config_tempest/services/orchestration.py", line 42, in set_default_tempest_options
 2019-06-13 05:18:36.253 66638 ERROR tempest conf.set(sec, 'region', conf.get('identity', 'region'))
 2019-06-13 05:18:36.253 66638 ERROR tempest File "/usr/lib64/python2.7/ConfigParser.py", line 618, in get
 2019-06-13 05:18:36.253 66638 ERROR tempest raise NoOptionError(option, section)
 2019-06-13 05:18:36.253 66638 ERROR tempest NoOptionError: No option 'region' in section: 'identity'
 2019-06-13 05:18:36.253 66638 ERROR tempest 
 Error while generating Tempest configuration, Please check keystone credentials
 Command 'discover-tempest-config --debug identity.uri [http://10.0.0.107:5000/v3] identity.admin_password V8OfgLkaOqqMDXi0It5xi9yjK --create' returned non-zero exit status 1



tempest rpm versions

[root@controller-0 heat-admin]# rpm -qa|grep tempest
 python2-neutron-tests-tempest-0.2.1-0.20180905004815.f785dd4.el7ost.noarch
 python2-sahara-tempest-0.7.0-0.20180925152245.bb23a5b.el7ost.noarch
 python-octavia-tests-tempest-golang-0.2.0-2.el7ost.x86_64
 python2-tempestconf-2.2.0-0.20190507153823.e0d5dd6.el7ost.noarch
 openstack-tempest-19.0.0-3.el7ost.noarch
 python2-manila-tests-tempest-0.1.1-0.20180830035250.4c91b6e.el7ost.noarch
 python2-cinder-tests-tempest-0.1.0-0.20180822115300.08a3851.el7ost.noarch
 python2-sahara-tests-tempest-0.7.0-0.20180925152245.bb23a5b.el7ost.noarch
 python2-octavia-tests-tempest-0.2.0-2.el7ost.noarch
 python2-tempest-19.0.0-3.el7ost.noarch

let me know if any more information needed.

Check the comment here:
https://bugzilla.redhat.com/show_bug.cgi?id=1716434#c4

Here's a review which added the code to openstack/tripleo-common which sets OS_REGION_NAME in overcloudrc file:
https://review.opendev.org/#/c/619236/

It should be backported to rocky and queens as well.

Patches backported in review:
Rocky: https://review.opendev.org/672787
Queens: https://review.opendev.org/672793

A follow-up information:
the region is defined in tempest-deployer-input.conf file (might be called a little differently based on the RHOS version) located under /home/stack/ directory on undercloud node.
In order to avoid the error about missing region, argument '--deployer-input <path to the tempest-deployer-input.conf file>' should be passed to discover-tempest-config as well.

Btw, the backports from comment #6 have been merged upstream.

Changing the DFG for this bug as patches are backported and already merged.

The main issue described here was caused by not passing deployer input file to discover-tempest-config which generated tempest.conf file. If the deployer input file was passed, the error woudn't occur. See comment #7. Based on that, I'm closing the bug as not a bug. If you're still experiencing the issue, feel free to reopen it.