Hi all, I'm having issue on debian based openstack install, for live-migrations with block migrate. Exact same setup with nfs shared storage, live-migration works OK.

Eveything used to work like a charm, but now I get this error in the logs : "Returning exception can only parse strings" on the destination host ;seems to be broken since update to nova v 2014.1.2-7~bpo70+1. Anybody has had the same issue ?

Log extract says :

2014-10-10 14:39:28.390 2944 ERROR oslo.messaging._drivers.common [-] Returning exception can only parse strings
Traceback (most recent call last):

  File "/usr/lib/python2.7/dist-packages/oslo/messaging/rpc/dispatcher.py", line 134, in _dispatch_and_reply
    incoming.message))

  File "/usr/lib/python2.7/dist-packages/oslo/messaging/rpc/dispatcher.py", line 177, in _dispatch
    return self._do_dispatch(endpoint, method, ctxt, args)

  File "/usr/lib/python2.7/dist-packages/oslo/messaging/rpc/dispatcher.py", line 123, in _do_dispatch
    result = getattr(endpoint, method)(ctxt, **new_args)

  File "/usr/lib/python2.7/dist-packages/nova/exception.py", line 88, in wrapped
    payload)

  File "/usr/lib/python2.7/dist-packages/nova/openstack/common/excutils.py", line 68, in __exit__
    six.reraise(self.type_, self.value, self.tb)

  File "/usr/lib/python2.7/dist-packages/nova/exception.py", line 71, in wrapped
    return f(self, context, *args, **kw)

  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 303, in decorated_function
    e, sys.exc_info())

  File "/usr/lib/python2.7/dist-packages/nova/openstack/common/excutils.py", line 68, in __exit__
    six.reraise(self.type_, self.value, self.tb)

  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 290, in decorated_function
    return function(self, context, *args, **kwargs)

  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 4473, in check_can_live_migrate_source
    block_device_info)

  File "/usr/lib/python2.7/dist-packages/nova/virt/libvirt/driver.py", line 4314, in check_can_live_migrate_source
    block_device_info)

  File "/usr/lib/python2.7/dist-packages/nova/virt/libvirt/driver.py", line 4382, in _assert_dest_node_has_enough_disk
    ret = self.get_instance_disk_info(instance['name'], block_device_info)

  File "/usr/lib/python2.7/dist-packages/nova/virt/libvirt/driver.py", line 4841, in get_instance_disk_info
    doc = etree.fromstring(xml)

  File "lxml.etree.pyx", line 2754, in lxml.etree.fromstring (src/lxml/lxml.etree.c:54631)

  File "parser.pxi", line 1575, in lxml.etree._parseMemoryDocument (src/lxml/lxml.etree.c:82710)

ValueError: can only parse strings
 to caller