title: Error when installing pbr
body: <p>I want to install openstack client on my machine running OSX 10.8.5. As a prerequisite, i need to install pbr. So, i did the following</p>
  
  <pre><code>git clone git://github.com/openstack-dev/pbr.git
  cd pbr
  sudo python setup.py install
  </code></pre>
  
  <p>But im getting the following error trace</p>
  
  <pre><code>Traceback (most recent call last):
    File "setup.py", line 22, in &lt;module&gt;
      **util.cfg_to_args())
    File "/Users/jimcgh/dev/pbr/pbr/util.py", line 241, in cfg_to_args
      pbr.hooks.setup_hook(config)
    File "/Users/jimcgh/dev/pbr/pbr/hooks/__init__.py", line 27, in setup_hook
      metadata_config.run()
    File "/Users/jimcgh/dev/pbr/pbr/hooks/base.py", line 29, in run
      self.hook()
    File "/Users/jimcgh/dev/pbr/pbr/hooks/metadata.py", line 28, in hook
      self.config['name'], self.config.get('version', None))
    File "/Users/jimcgh/dev/pbr/pbr/packaging.py", line 817, in get_version
      version = _get_version_from_git(pre_version)
    File "/Users/jimcgh/dev/pbr/pbr/packaging.py", line 776, in _get_version_from_git
      "git --git-dir=\"" + git_dir + "\" describe --always").replace(
    File "/Users/jimcgh/dev/pbr/pbr/packaging.py", line 220, in _run_shell_command
      stderr=err_location)
    File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 679, in __init__
      errread, errwrite)
    File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 1228, in _execute_child
      raise child_exception
  TypeError: must be encoded string without NULL bytes, not str
  </code></pre>
  
  <p>How can i fix this ?</p>
  
  <p>Please help.
  Thank You</p>