Only the file /usr/share/heat/heat-dist.conf is included in the package openstack-heat. The file /etc/heat/heat.conf is not included in the package and /usr/share/heat/heat-dist.conf is not really complete. Can you please add the file genereated with tox -egenconfig (https://github.com/openstack/heat/blob/master/etc/heat/README-heat.conf.txt) to openstack-heat?
This has been fixed, see review https://review.gerrithub.io/#/c/231959/