I am not sure whether this bug is fixed. I can reproduce it on master branch.

my test environment is setup with commit 172d4a00ce609da7ea6d8d97f635e6c9afecb373.


2015-08-12 23:23:15.793 INFO nova.compute.manager [req-6e6eb653-cb52-47a2-93e5-d520633e4e10 admin admin] [instance: 0030bb4e-10f3-4300-9ab7-2a2bd609678f] Detach volume fe82d173-1500-4bfb-a541-3046b46c8be0 from mountpoint /dev/vdb
 ----BlockDeviceMapping(boot_index=None,connection_info=None,created_at=2015-08-12T13:38:16Z,delete_on_termination=False,deleted=False,deleted_at=None,destination_type='volume',device_name='/dev/vdb',device_type=None,disk_bus=None,guest_format=None,id=2685,image_id=None,instance=<?>,instance_uuid=0030bb4e-10f3-4300-9ab7-2a2bd609678f,no_device=False,snapshot_id=None,source_type='volume',updated_at=None,volume_id='fe82d173-1500-4bfb-a541-3046b46c8be0',volume_size=None) --- (This is printed by me)
2015-08-12 23:23:15.808 ERROR oslo_messaging.rpc.dispatcher [req-6e6eb653-cb52-47a2-93e5-d520633e4e10 admin admin] Exception during message handling: <type 'NoneType'> can't be decoded
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher Traceback (most recent call last):
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher   File "/usr/local/lib/python2.7/dist-packages/oslo_messaging/rpc/dispatcher.py", line 142, in _dispatch_and_reply
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher     executor_callback))
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher   File "/usr/local/lib/python2.7/dist-packages/oslo_messaging/rpc/dispatcher.py", line 186, in _dispatch
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher     executor_callback)
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher   File "/usr/local/lib/python2.7/dist-packages/oslo_messaging/rpc/dispatcher.py", line 129, in _do_dispatch
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher     result = func(ctxt, **new_args)
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher   File "/opt/stack/nova/nova/exception.py", line 89, in wrapped
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher     payload)
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher   File "/usr/local/lib/python2.7/dist-packages/oslo_utils/excutils.py", line 119, in __exit__
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher     six.reraise(self.type_, self.value, self.tb)
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher   File "/opt/stack/nova/nova/exception.py", line 72, in wrapped
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher     return f(self, context, *args, **kw)
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher   File "/opt/stack/nova/nova/compute/manager.py", line 364, in decorated_function
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher     kwargs['instance'], e, sys.exc_info())
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher   File "/usr/local/lib/python2.7/dist-packages/oslo_utils/excutils.py", line 119, in __exit__
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher     six.reraise(self.type_, self.value, self.tb)
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher   File "/opt/stack/nova/nova/compute/manager.py", line 352, in decorated_function
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher     return function(self, context, *args, **kwargs)
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher   File "/opt/stack/nova/nova/compute/manager.py", line 4594, in detach_volume
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher     self._detach_volume(context, volume_id, instance)
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher   File "/opt/stack/nova/nova/compute/manager.py", line 4577, in _detach_volume
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher     self._driver_detach_volume(context, instance, bdm)
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher   File "/opt/stack/nova/nova/compute/manager.py", line 4512, in _driver_detach_volume
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher     connection_info = jsonutils.loads(bdm.connection_info)
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher   File "/usr/local/lib/python2.7/dist-packages/oslo_serialization/jsonutils.py", line 214, in loads
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher     return json.loads(encodeutils.safe_decode(s, encoding), **kwargs)
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher   File "/usr/local/lib/python2.7/dist-packages/oslo_utils/encodeutils.py", line 33, in safe_decode
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher     raise TypeError("%s can't be decoded" % type(text))
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher TypeError: <type 'NoneType'> can't be decoded
2015-08-12 23:23:15.808 136462 ERROR oslo_messaging.rpc.dispatcher