diff --git a/openstack_dashboard/utils/settings.py b/openstack_dashboard/utils/settings.py
index <HASH>..<HASH> 100644
--- a/openstack_dashboard/utils/settings.py
+++ b/openstack_dashboard/utils/settings.py
@@ -117,7 +117,7 @@ def update_dashboards(modules, horizon_config, installed_apps):
 
     horizon_config['panel_customization'] = panel_customization
     horizon_config['dashboards'] = tuple(dashboards)
-    horizon_config['exceptions'].update(exceptions)
+    horizon_config.setdefault('exceptions', {}).update(exceptions)
     horizon_config.update(update_horizon_config)
     horizon_config.setdefault('angular_modules', []).extend(angular_modules)
     horizon_config.setdefault('js_files', []).extend(js_files)
Permit 'exceptions' to be omitted from HORIZON_CONFIG

Without this change, if HORIZON_CONFIG is defined in local_settings.py
and does not have an 'exceptions' entry, then horizon throws and
exception and fails to start.

Change-Id: I<I>f<I>d1c<I>ac<I>bdcc<I>d5acb2a0b<I>
Closes-Bug: #<I>