command : openstack user list
Traceback (most recent call last):
  File "/bin/openstack", line 7, in <module>
    from openstackclient.shell import main
  File "/usr/lib/python2.7/site-packages/openstackclient/__init__.py", line 16, in <module>
    import pbr.version
  File "/usr/lib/python2.7/site-packages/pbr/version.py", line 25, in <module>
    import pkg_resources
  File "/usr/lib/python2.7/site-packages/pkg_resources/__init__.py", line 41, in <module>
    import inspect
  File "/usr/lib64/python2.7/inspect.py", line 39, in <module>
    import tokenize
  File "/usr/lib64/python2.7/tokenize.py", line 30, in <module>
    from token import *
  File "/opt/stack/keystone/token/__init__.py", line 15, in <module>
    from keystone.token import controllers  # noqa
  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 18, in <module>
    from keystone.common import utils
  File "/opt/stack/keystone/keystone/common/utils.py", line 28, in <module>
    from oslo_log import log
  File "/usr/lib/python2.7/site-packages/oslo_log/log.py", line 42, in <module>
    from oslo_config import cfg
  File "/usr/lib/python2.7/site-packages/oslo_config/cfg.py", line 458, in <module>
    import debtcollector
  File "/usr/lib/python2.7/site-packages/debtcollector/__init__.py", line 19, in <module>
    __version__ = pbr.version.VersionInfo(
AttributeError: 'module' object has no attribute 'version'