SOLVED:ERROR nova.virt.libvirt.driver [-] Connection to libvirt failed: Failed to connect socket to '/var/run/libvirt/libvirt-sock' Permission denied

Fix
====
http://wiki.libvirt.org/page/Failed_to_connect_to_the_hypervisor

a)
sudo vim /etc/libvirt/libvirtd.conf
unix_sock_group = "libvirtd"
unix_sock_rw_perms = "0770"

b)
sudo service libvirt-bin restart

Error:
======
2014-04-18 01:09:15.254 ERROR nova.virt.libvirt.driver [-] Connection to libvirt failed: Failed to connect socket to '/var/run/libvirt/libvirt-sock'
: Permission denied
2014-04-18 01:09:15.254 TRACE nova.virt.libvirt.driver Traceback (most recent call last):
2014-04-18 01:09:15.254 TRACE nova.virt.libvirt.driver   File "/opt/stack/nova/nova/virt/libvirt/driver.py", line 677, in _connect
2014-04-18 01:09:15.254 TRACE nova.virt.libvirt.driver     return libvirt.openAuth(uri, auth, flags)
2014-04-18 01:09:15.254 TRACE nova.virt.libvirt.driver   File "/usr/lib/python2.7/dist-packages/libvirt.py", line 102, in openAuth
2014-04-18 01:09:15.254 TRACE nova.virt.libvirt.driver     if ret is None:raise libvirtError('virConnectOpenAuth() failed')
2014-04-18 01:09:15.254 TRACE nova.virt.libvirt.driver libvirtError: Failed to connect socket to '/var/run/libvirt/libvirt-sock': Permission denied
2014-04-18 01:09:15.254 TRACE nova.virt.libvirt.driver