keystoneclient throws exception when loading auth_ref dictionary

Keystoneclient auth_ref intialization fails with a auth_ref just previously retrieved:

example:

#!/usr/bin/env python
from keystoneclient import access
from keystoneclient.v2_0 import client

kc = client.Client(
    username='heckj', password='****',
    auth_url='http://localhost:5000/v2.0',
    debug=True)

kc.authenticate(tenant_name='my-project')

cached_token = json.dumps(kc.auth_ref)
print "--"
print "cached token: %s" % cached_token

loaded_token_dict = json.loads(cached_token)
ai = access.AccessInfo(loaded_token_dict)
print "--"
print "ai is %s" % ai
print "ai.scoped is %s" % ai.scoped
print "ai.auth_url is %s" % ai.auth_url

kc2 = client.Client(auth_ref=loaded_token_dict)