Bingo:

http://logs.openstack.org/15/109115/1/check/check-tempest-dsvm-full/168a5dd/logs/screen-n-cpu.txt.gz?level=TRACE#_2014-07-24_00_57_06_425

2014-07-24 00:57:06.425 ERROR oslo.messaging.rpc.dispatcher [req-cd0800cd-de93-40f4-86ca-9f2ac3a1fe88 TestEncryptedCinderVolumes-1712166565 TestEncryptedCinderVolumes-692029700] Exception during message handling: <type 'NoneType'> can't be decoded
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher Traceback (most recent call last):
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher   File "/usr/local/lib/python2.7/dist-packages/oslo/messaging/rpc/dispatcher.py", line 134, in _dispatch_and_reply
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher     incoming.message))
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher   File "/usr/local/lib/python2.7/dist-packages/oslo/messaging/rpc/dispatcher.py", line 177, in _dispatch
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher     return self._do_dispatch(endpoint, method, ctxt, args)
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher   File "/usr/local/lib/python2.7/dist-packages/oslo/messaging/rpc/dispatcher.py", line 123, in _do_dispatch
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher     result = getattr(endpoint, method)(ctxt, **new_args)
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher   File "/opt/stack/new/nova/nova/compute/manager.py", line 406, in decorated_function
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher     return function(self, context, *args, **kwargs)
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher   File "/opt/stack/new/nova/nova/exception.py", line 88, in wrapped
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher     payload)
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher   File "/opt/stack/new/nova/nova/openstack/common/excutils.py", line 82, in __exit__
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher     six.reraise(self.type_, self.value, self.tb)
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher   File "/opt/stack/new/nova/nova/exception.py", line 71, in wrapped
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher     return f(self, context, *args, **kw)
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher   File "/opt/stack/new/nova/nova/compute/manager.py", line 291, in decorated_function
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher     pass
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher   File "/opt/stack/new/nova/nova/openstack/common/excutils.py", line 82, in __exit__
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher     six.reraise(self.type_, self.value, self.tb)
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher   File "/opt/stack/new/nova/nova/compute/manager.py", line 277, in decorated_function
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher     return function(self, context, *args, **kwargs)
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher   File "/opt/stack/new/nova/nova/compute/manager.py", line 319, in decorated_function
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher     kwargs['instance'], e, sys.exc_info())
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher   File "/opt/stack/new/nova/nova/openstack/common/excutils.py", line 82, in __exit__
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher     six.reraise(self.type_, self.value, self.tb)
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher   File "/opt/stack/new/nova/nova/compute/manager.py", line 307, in decorated_function
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher     return function(self, context, *args, **kwargs)
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher   File "/opt/stack/new/nova/nova/compute/manager.py", line 4363, in detach_volume
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher     self._detach_volume(context, instance, bdm)
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher   File "/opt/stack/new/nova/nova/compute/manager.py", line 4309, in _detach_volume
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher     connection_info = jsonutils.loads(bdm.connection_info)
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher   File "/opt/stack/new/nova/nova/openstack/common/jsonutils.py", line 172, in loads
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher     return json.loads(strutils.safe_decode(s, encoding), **kwargs)
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher   File "/opt/stack/new/nova/nova/openstack/common/strutils.py", line 112, in safe_decode
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher     raise TypeError("%s can't be decoded" % type(text))
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher TypeError: <type 'NoneType'> can't be decoded
2014-07-24 00:57:06.425 21003 TRACE oslo.messaging.rpc.dispatcher