Just to say, seeing the same issue with CentOS Linux release 7.6.1810 (Core) and OSA 18.1.4. Also tried with the latest checkout of "stable/rocky" OSA with same result.

Attempted to build using "distro" install method and RDO packages, as well as "source" install, both with the same result. 

Error is as follows:

[...]
failed: [infra1_horizon_container-059e6df0] (item={u'src': u'/usr/share/openstack-dashboard/heat_dashboard/local_settings.d/_1699_orchestration_settings.py
', u'state': u'file', u'path': u'/usr/share/openstack-dashboard/openstack_dashboard/local/local_settings.d/_1699_orchestration_settings.py'}) => {"changed"
: false, "item": {"path": "/usr/share/openstack-dashboard/openstack_dashboard/local/local_settings.d/_1699_orchestration_settings.py", "src": "/usr/share/o
penstack-dashboard/heat_dashboard/local_settings.d/_1699_orchestration_settings.py", "state": "file"}, "msg": "file (/usr/share/openstack-dashboard/opensta
ck_dashboard/local/local_settings.d/_1699_orchestration_settings.py) is absent, cannot continue", "path": "/usr/share/openstack-dashboard/openstack_dashboa
rd/local/local_settings.d/_1699_orchestration_settings.py", "state": "absent"}
ok: [infra2_horizon_container-386c2dd8] => (item={u'src': u'/usr/share/openstack-dashboard/heat_dashboard/enabled/_1650_project_template_generator_panel.py
', u'state': u'file', u'path': u'/usr/share/openstack-dashboard/openstack_dashboard/local/enabled/_1650_project_template_generator_panel.py'})
failed: [infra1_horizon_container-059e6df0] (item={u'src': u'/usr/share/openstack-dashboard/heat_dashboard/conf/heat_policy.json', u'state': u'file', u'pat
h': u'/usr/share/openstack-dashboard/openstack_dashboard/conf/heat_policy.json'}) => {"changed": false, "item": {"path": "/usr/share/openstack-dashboard/op
enstack_dashboard/conf/heat_policy.json", "src": "/usr/share/openstack-dashboard/heat_dashboard/conf/heat_policy.json", "state": "file"}, "msg": "file (/us
r/share/openstack-dashboard/openstack_dashboard/conf/heat_policy.json) is absent, cannot continue", "path": "/usr/share/openstack-dashboard/openstack_dashboard/conf/heat_policy.json", "state": "absent"}
failed: [infra3_horizon_container-746d175f] (item={u'src': u'/usr/share/openstack-dashboard/heat_dashboard/local_settings.d/_1699_orchestration_settings.py', u'state': u'file', u'path': u'/usr/share/openstack-dashboard/openstack_dashboard/local/local_settings.d/_1699_orchestration_settings.py'}) => {"changed": false, "item": {"path": "/usr/share/openstack-dashboard/openstack_dashboard/local/local_settings.d/_1699_orchestration_settings.py", "src": "/usr/share/openstack-dashboard/heat_dashboard/local_settings.d/_1699_orchestration_settings.py", "state": "file"}, "msg": "file (/usr/share/openstack-dashboard/openstack_dashboard/local/local_settings.d/_1699_orchestration_settings.py) is absent, cannot continue", "path": "/usr/share/openstack-dashboard/openstack_dashboard/local/local_settings.d/_1699_orchestration_settings.py", "state": "absent"}
failed: [infra2_horizon_container-386c2dd8] (item={u'src': u'/usr/share/openstack-dashboard/heat_dashboard/local_settings.d/_1699_orchestration_settings.py', u'state': u'file', u'path': u'/usr/share/openstack-dashboard/openstack_dashboard/local/local_settings.d/_1699_orchestration_settings.py'}) => {"changed": false, "item": {"path": "/usr/share/openstack-dashboard/openstack_dashboard/local/local_settings.d/_1699_orchestration_settings.py", "src": "/usr/share/openstack-dashboard/heat_dashboard/local_settings.d/_1699_orchestration_settings.py", "state": "file"}, "msg": "file (/usr/share/openstack-dashboard/openstack_dashboard/local/local_settings.d/_1699_orchestration_settings.py) is absent, cannot continue", "path": "/usr/share/openstack-dashboard/openstack_dashboard/local/local_settings.d/_1699_orchestration_settings.py", "state": "absent"}
failed: [infra3_horizon_container-746d175f] (item={u'src': u'/usr/share/openstack-dashboard/heat_dashboard/conf/heat_policy.json', u'state': u'file', u'path': u'/usr/share/openstack-dashboard/openstack_dashboard/conf/heat_policy.json'}) => {"changed": false, "item": {"path": "/usr/share/openstack-dashboard/openstack_dashboard/conf/heat_policy.json", "src": "/usr/share/openstack-dashboard/heat_dashboard/conf/heat_policy.json", "state": "file"}, "msg": "file (/usr/share/openstack-dashboard/openstack_dashboard/conf/heat_policy.json) is absent, cannot continue", "path": "/usr/share/openstack-dashboard/openstack_dashboard/conf/heat_policy.json", "state": "absent"}
changed: [infra1_horizon_container-059e6df0] => (item={u'src': u'/usr/share/openstack-dashboard/designatedashboard/enabled/_1710_project_dns_panel_group.py', u'state': u'absent', u'path': u'/usr/share/openstack-dashboard/openstack_dashboard/local/enabled/_1710_project_dns_panel_group.py'})
failed: [infra2_horizon_container-386c2dd8] (item={u'src': u'/usr/share/openstack-dashboard/heat_dashboard/conf/heat_policy.json', u'state': u'file', u'path': u'/usr/share/openstack-dashboard/openstack_dashboard/conf/heat_policy.json'}) => {"changed": false, "item": {"path": "/usr/share/openstack-dashboard/openstack_dashboard/conf/heat_policy.json", "src": "/usr/share/openstack-dashboard/heat_dashboard/conf/heat_policy.json", "state": "file"}, "msg": "file (/usr/share/openstack-dashboard/openstack_dashboard/conf/heat_policy.json) is absent, cannot continue", "path": "/usr/share/openstack-dashboard/openstack_dashboard/conf/heat_policy.json", "state": "absent"}
[...]