The error was thrown out when run:

/opt/stack/keystone/bin/keystone-manage db_syn

Traceback (most recent call last):
  File "/opt/stack/keystone/bin/keystone-manage", line 30, in <module>
    from keystone import cli
  File "/opt/stack/keystone/keystone/cli.py", line 31, in <module>
    from keystone import token
  File "/opt/stack/keystone/keystone/token/__init__.py", line 15, in <module>
    from keystone.token import controllers  # noqa
  File "/opt/stack/keystone/keystone/token/controllers.py", line 31, in <module>
    from keystone.token import provider
  File "/opt/stack/keystone/keystone/token/provider.py", line 37, in <module>
    from keystone.token import persistence
  File "/opt/stack/keystone/keystone/token/persistence/__init__.py", line 13, in <module>
    from keystone.token.persistence.core import *  # noqa
  File "/opt/stack/keystone/keystone/token/persistence/core.py", line 44, in <module>
    class PersistenceManager(manager.Manager):
  File "/opt/stack/keystone/keystone/token/persistence/core.py", line 58, in PersistenceManager
    what='token_api.unique_id')
  File "/opt/stack/keystone/keystone/openstack/common/versionutils.py", line 128, in __call__
    @six.wraps(func_or_cls)
AttributeError: 'module' object has no attribute 'wraps'

Looks like something related to package six. But I have the latest installed:

$ pip show six
---
Name: six
Version: 1.8.0
Location: /usr/local/lib/python2.7/dist-packages
Requires: