pyrax: Installation error: [Exception: Versioning for this project requires...]

I installed for python 2.7 on OS X using both (1) the standard pip install pyrax and (2) the git version.

Both ways, I receive the following error:

Suggestions would be helpul. Thanks, ~John

>>> import pyrax
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Library/Python/2.7/site-packages/pyrax/__init__.py", line 51, in <module>
    from .identity import *
  File "/Library/Python/2.7/site-packages/pyrax/identity/keystone_identity.py", line 7, in <module>
    from ..base_identity import BaseIdentity
  File "/Library/Python/2.7/site-packages/pyrax/base_identity.py", line 20, in <module>
    from pyrax import exceptions as exc
  File "/Library/Python/2.7/site-packages/pyrax/exceptions.py", line 22, in <module>
    from novaclient import exceptions as _nova_exceptions
  File "/Library/Python/2.7/site-packages/novaclient/__init__.py", line 18, in <module>
    __version__ = pbr.version.VersionInfo('python-novaclient').version_string()
  File "/Library/Python/2.7/site-packages/pbr/version.py", line 78, in version_string
    for part in self.release_string().split('.'):
  File "/Library/Python/2.7/site-packages/pbr/version.py", line 70, in release_string
    self.release = self._get_version_from_pkg_resources()
  File "/Library/Python/2.7/site-packages/pbr/version.py", line 62, in _get_version_from_pkg_resources
    return packaging.get_version(self.package)
  File "/Library/Python/2.7/site-packages/pbr/packaging.py", line 870, in get_version
    raise Exception("Versioning for this project requires either an sdist"
Exception: Versioning for this project requires either an sdist tarball, or access to an upstream git repository. Are you sure that git is installed?