Traceback (most recent call last):
  File "/etc/munin/plugins/libvirt", line 51, in <module>
    conn = libvirt.openReadOnly(uri)
  File "/usr/lib/python2.5/site-packages/libvirt.py", line 148, in openReadOnly
    if ret is None:raise libvirtError('virConnectOpenReadOnly() failed')
libvirtError: virConnectOpenReadOnly() failed