as a non-root user:
cd /usr/share/openstack-tempest-kilo
source keystonerc_admin # from packstack --allinone
tools/config_tempest.py --debug --out /tmp/tempest.conf identity.uri
$OS_AUTH_URL identity.admin_password $OS_PASSWORD --create
UPDATE, this worked:
tools/config_tempest.py --out /tmp/tempest.conf --create identity.uri
$OS_AUTH_URL identity.admin_password $OS_PASSWORD scenario.img_dir
/tmp