Updated openstack/openstack
Project: openstack/horizon  d55368b0a12547a772a58f535e06fcd81f85f93d

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: I74f244974982d1c56ac36bdcc032d5acb2a0b274
Closes-Bug: #1368361