Docker container-create fails with Unicode is not supported

[Dane LeBlanc]

If a docker swarm baymodel and docker swarm bay are created according to instructions listed in the Magnum quick-start guide:
    https://github.com/openstack/magnum/blob/master/doc/source/dev/dev-quickstart.rst#building-and-using-a-swarm-bay
and then a docker container is created, e.g.:
    magnum container-create --name testcontainer --image cirros --bay swarmbay --command ping -c 4 10.86.7.2
then the container-create operation fails with the following error generated on the command line:
    ERROR: Docker internal Error: decoding Unicode is not supported (HTTP 500)

The following errors are seen in the magnum conductor process log:

2015-07-06 14:06:31.658 ERROR magnum.conductor.handlers.docker_conductor [req-695978bb-ccb2-42d5-a612-71083f9e3ed8 admin admin] Error while connect to docker container ff8a6da2-2987-4916-8320-73a5ea506743: decoding Unicode is not supported
2015-07-06 14:06:31.658 TRACE magnum.conductor.handlers.docker_conductor Traceback (most recent call last):
2015-07-06 14:06:31.658 TRACE magnum.conductor.handlers.docker_conductor File "/opt/stack/magnum/magnum/conductor/handlers/docker_conductor.py", line 62, in wrapped
2015-07-06 14:06:31.658 TRACE magnum.conductor.handlers.docker_conductor return f(self, context, *args, **kwargs)
2015-07-06 14:06:31.658 TRACE magnum.conductor.handlers.docker_conductor File "/opt/stack/magnum/magnum/conductor/handlers/docker_conductor.py", line 125, in container_create
2015-07-06 14:06:31.658 TRACE magnum.conductor.handlers.docker_conductor docker.inspect_image(self._encode_utf8(container.image))
2015-07-06 14:06:31.658 TRACE magnum.conductor.handlers.docker_conductor File "/opt/stack/magnum/magnum/conductor/handlers/docker_conductor.py", line 92, in _encode_utf8
2015-07-06 14:06:31.658 TRACE magnum.conductor.handlers.docker_conductor return six.u(value).encode('utf-8')
2015-07-06 14:06:31.658 TRACE magnum.conductor.handlers.docker_conductor File "/usr/local/lib/python2.7/dist-packages/six.py", line 621, in u
2015-07-06 14:06:31.658 TRACE magnum.conductor.handlers.docker_conductor return unicode(s.replace(r'\\', r'\\\\'), "unicode_escape")
2015-07-06 14:06:31.658 TRACE magnum.conductor.handlers.docker_conductor TypeError: decoding Unicode is not supported
2015-07-06 14:06:31.658 TRACE magnum.conductor.handlers.docker_conductor
2015-07-06 14:06:31.660 ERROR oslo_messaging.rpc.dispatcher [req-695978bb-ccb2-42d5-a612-71083f9e3ed8 admin admin] Exception during message handling: Docker internal Error: decoding Unicode is not supported
2015-07-06 14:06:31.660 TRACE oslo_messaging.rpc.dispatcher Traceback (most recent call last):
2015-07-06 14:06:31.660 TRACE oslo_messaging.rpc.dispatcher File "/usr/local/lib/python2.7/dist-packages/oslo_messaging/rpc/dispatcher.py", line 146, in _dispatch_and_reply
2015-07-06 14:06:31.660 TRACE oslo_messaging.rpc.dispatcher executor_callback))
2015-07-06 14:06:31.660 TRACE oslo_messaging.rpc.dispatcher File "/usr/local/lib/python2.7/dist-packages/oslo_messaging/rpc/dispatcher.py", line 190, in _dispatch
2015-07-06 14:06:31.660 TRACE oslo_messaging.rpc.dispatcher executor_callback)
2015-07-06 14:06:31.660 TRACE oslo_messaging.rpc.dispatcher File "/usr/local/lib/python2.7/dist-packages/oslo_messaging/rpc/dispatcher.py", line 134, in _do_dispatch
2015-07-06 14:06:31.660 TRACE oslo_messaging.rpc.dispatcher result = func(ctxt, **new_args)
2015-07-06 14:06:31.660 TRACE oslo_messaging.rpc.dispatcher File "/opt/stack/magnum/magnum/conductor/handlers/docker_conductor.py", line 71, in wrapped
2015-07-06 14:06:31.660 TRACE oslo_messaging.rpc.dispatcher "Docker internal Error: %s" % str(e))
2015-07-06 14:06:31.660 TRACE oslo_messaging.rpc.dispatcher ContainerException: Docker internal Error: decoding Unicode is not supported
2015-07-06 14:06:31.660 TRACE oslo_messaging.rpc.dispatcher