OpenStack "libvirtError: internal error no supported architecture for os type 'hvm'

Fix
====
a)
#sudo vim /etc/nova/nova-compute.conf
[DEFAULT]
libvirt_type=qemu
compute_driver=libvirt.LibvirtDriver

b)
#sudo service nova-compute restart

Error
======
2014-11-13 16:46:35.880 1943 INFO nova.scheduler.filter_scheduler [req-d3d831b7-d5bd-43d8-9a95-39914b90fe3b f62fed25125b40c59b290e4b9f820ccb ead267fc9a9e451ba390143c62d1f00d] Attempting to build 1 instance(s) uuids: [u'c792d53c-e057-4d43-b088-b253165fb603']
2014-11-13 16:46:35.913 1943 INFO nova.scheduler.filter_scheduler [req-d3d831b7-d5bd-43d8-9a95-39914b90fe3b f62fed25125b40c59b290e4b9f820ccb ead267fc9a9e451ba390143c62d1f00d] Choosing host WeighedHost [host: contrailsys, weight: 4214.0] for instance c792d53c-e057-4d43-b088-b253165fb603
2014-11-13 16:46:36.193 1943 INFO nova.openstack.common.rpc.common [req-d3d831b7-d5bd-43d8-9a95-39914b90fe3b f62fed25125b40c59b290e4b9f820ccb ead267fc9a9e451ba390143c62d1f00d] Connected to AMQP server on 127.0.0.1:5672
2014-11-13 16:46:45.890 1943 INFO nova.scheduler.filter_scheduler [req-d3d831b7-d5bd-43d8-9a95-39914b90fe3b f62fed25125b40c59b290e4b9f820ccb ead267fc9a9e451ba390143c62d1f00d] Attempting to build 1 instance(s) uuids: [u'c792d53c-e057-4d43-b088-b253165fb603']
2014-11-13 16:46:45.894 1943 ERROR nova.scheduler.filter_scheduler [req-d3d831b7-d5bd-43d8-9a95-39914b90fe3b f62fed25125b40c59b290e4b9f820ccb ead267fc9a9e451ba390143c62d1f00d] [instance: c792d53c-e057-4d43-b088-b253165fb603] Error from last host: contrailsys (node contrailsys): [u'Traceback (most recent call last):\n', u'  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 1040, in _build_instance\n    set_access_ip=set_access_ip)\n', u'  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 1413, in _spawn\n    LOG.exception(_(\'Instance failed to spawn\'), instance=instance)\n', u'  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 1410, in _spawn\n    block_device_info)\n', u'  File "/usr/lib/python2.7/dist-packages/nova/virt/libvirt/driver.py", line 2071, in spawn\n    block_device_info, context=context)\n', u'  File "/usr/lib/python2.7/dist-packages/nova/virt/libvirt/driver.py", line 3225, in _create_domain_and_network\n    domain = self._create_domain(xml, instance=instance, power_on=power_on)\n', u'  File "/usr/lib/python2.7/dist-packages/nova/virt/libvirt/driver.py", line 3159, in _create_domain\n    raise e\n', u"libvirtError: internal error no supported architecture for os type 'hvm'\n"]
2014-11-13 16:46:45.940 1943 WARNING nova.scheduler.driver [req-d3d831b7-d5bd-43d8-9a95-39914b90fe3b f62fed25125b40c59b290e4b9f820ccb ead267fc9a9e451ba390143c62d1f00d] [instance: c792d53c-e057-4d43-b088-b253165fb603] Setting instance to ERROR state.