Open Stack

When I install openstack mitaka version, after this step:
https://docs.openstack.org/mitaka/install-guide-ubuntu/keystone-install.html
When I run 'keystone', I got this error. Why?

gateway at ubuntu-1404-64-20160922:~$ keystone -v
Traceback (most recent call last):
  File "/usr/bin/keystone", line 6, in <module>
    from keystoneclient.shell import main
  File "/usr/local/lib/python2.7/dist-packages/keystoneclient/__init__.py",
line 33, in <module>
    import pbr.version
  File "/usr/local/lib/python2.7/dist-packages/pbr/version.py", line 25, in
<module>
    import pkg_resources
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py",
line 3019, in <module>
    @_call_aside
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py",
line 3003, in _call_aside
    f(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py",
line 3047, in _initialize_master_working_set
    for dist in working_set
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py",
line 3047, in <genexpr>
    for dist in working_set
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py",
line 2577, in activate
    declare_namespace(pkg)
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py",
line 2151, in declare_namespace
    _handle_ns(packageName, path_item)
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py",
line 2086, in _handle_ns
    loader.load_module(packageName)
  File "/usr/lib/python2.7/pkgutil.py", line 246, in load_module
    mod = imp.load_module(fullname, self.file, self.filename, self.etc)
  File "/usr/lib/python2.7/dist-packages/openstack/__init__.py", line 18,
in <module>
    __version__ = pbr.version.VersionInfo('openstacksdk').version_string()
AttributeError: 'module' object has no attribute 'version'
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