How to fix libvirtError: authentication failed: no agent is available to authenticate

Fix:

$ sudo vim  /etc/libvirt/libvirtd.conf

# If the unix_sock_rw_perms are changed you may wish to enable
# an authentication mechanism here
auth_unix_rw = "none"

==========Error==========

2017-03-03 15:54:38.088 DEBUG nova.virt.libvirt.host [-] Connecting to libvirt: qemu:///system from (pid=6113) _get_new_connection /opt/stack/nova/no
va/virt/libvirt/host.py:368
2017-03-03 15:54:38.114 ERROR nova.virt.libvirt.host [-] Connection to libvirt failed: authentication failed: no agent is available to authenticate
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host Traceback (most recent call last):
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host   File "/opt/stack/nova/nova/virt/libvirt/host.py", line 454, in get_connection
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host     conn = self._get_connection()
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host   File "/opt/stack/nova/nova/virt/libvirt/host.py", line 437, in _get_connection
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host     {'msg': ex})
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host   File "/usr/local/lib/python2.7/dist-packages/oslo_utils/excutils.py", line 220, in __exit__
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host     self.force_reraise()
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host   File "/usr/local/lib/python2.7/dist-packages/oslo_utils/excutils.py", line 196, in force_reraise
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host     six.reraise(self.type_, self.value, self.tb)
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host   File "/opt/stack/nova/nova/virt/libvirt/host.py", line 426, in _get_connection
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host     self._wrapped_conn = self._get_new_connection()
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host   File "/opt/stack/nova/nova/virt/libvirt/host.py", line 371, in _get_new_connection
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host     wrapped_conn = self._connect(self._uri, self._read_only)
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host   File "/opt/stack/nova/nova/virt/libvirt/host.py", line 227, in _connect
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host     libvirt.openAuth, uri, auth, flags)
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host   File "/usr/local/lib/python2.7/dist-packages/eventlet/tpool.py", line 144, in proxy_call
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host     rv = execute(f, *args, **kwargs)
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host   File "/usr/local/lib/python2.7/dist-packages/eventlet/tpool.py", line 125, in execute
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host     six.reraise(c, e, tb)
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host   File "/usr/local/lib/python2.7/dist-packages/eventlet/tpool.py", line 83, in tworker
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host     rv = meth(*args, **kwargs)
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host   File "/usr/local/lib/python2.7/dist-packages/libvirt.py", line 105, in openAuth
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host     if ret is None:raise libvirtError('virConnectOpenAuth() failed')
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host libvirtError: authentication failed: no agent is available to authenticate
2017-03-03 15:54:38.114 TRACE nova.virt.libvirt.host
2017-03-03 15:54:38.143 INFO nova.virt.libvirt.driver [-] Connection event '0' reason 'Failed to connect to libvirt: authentication failed: no agent is available to authenticate'
2017-03-03 15:54:38.145 DEBUG oslo_messa

=====================

2017-03-03 15:35:31.040 ERROR oslo_service.service [req-d687bfd4-f9d8-4031-a2bb-b6df6a9abc12 None None] Error starting thread.
2017-03-03 15:35:31.040 TRACE oslo_service.service Traceback (most recent call last):
2017-03-03 15:35:31.040 TRACE oslo_service.service   File "/usr/local/lib/python2.7/dist-packages/oslo_service/service.py", line 722, in run_service
2017-03-03 15:35:31.040 TRACE oslo_service.service     service.start()
2017-03-03 15:35:31.040 TRACE oslo_service.service   File "/opt/stack/nova/nova/service.py", line 144, in start
2017-03-03 15:35:31.040 TRACE oslo_service.service     self.manager.init_host()
2017-03-03 15:35:31.040 TRACE oslo_service.service   File "/opt/stack/nova/nova/compute/manager.py", line 1138, in init_host
2017-03-03 15:35:31.040 TRACE oslo_service.service     self.driver.init_host(host=self.host)
2017-03-03 15:35:31.040 TRACE oslo_service.service   File "/opt/stack/nova/nova/virt/libvirt/driver.py", line 469, in init_host
2017-03-03 15:35:31.040 TRACE oslo_service.service     self._do_quality_warnings()
2017-03-03 15:35:31.040 TRACE oslo_service.service   File "/opt/stack/nova/nova/virt/libvirt/driver.py", line 446, in _do_quality_warnings
2017-03-03 15:35:31.040 TRACE oslo_service.service     caps = self._host.get_capabilities()
2017-03-03 15:35:31.040 TRACE oslo_service.service   File "/opt/stack/nova/nova/virt/libvirt/host.py", line 639, in get_capabilities
2017-03-03 15:35:31.040 TRACE oslo_service.service     xmlstr = self.get_connection().getCapabilities()
2017-03-03 15:35:31.040 TRACE oslo_service.service   File "/opt/stack/nova/nova/virt/libvirt/host.py", line 463, in get_connection
2017-03-03 15:35:31.040 TRACE oslo_service.service     raise exception.HypervisorUnavailable(host=CONF.host)
2017-03-03 15:35:31.040 TRACE oslo_service.service HypervisorUnavailable: Connection to the hypervisor is broken on host: masterneutron
2017-03-03 15:35:31.040 TRACE oslo_service.service
2017-03-03 15:35:31.051 DEBUG oslo_concurrency.lockutils [req-b130d18f-6c7f-4c3c-b4e4-18e057e647b0 None None] Acquired semaphore "singleton_lock" from (pid=5403) lock /usr/local/lib/python2.7/dist-packages/oslo