$ PBR_VERSION=1.2.3 python setup.py build_sphinx
running build_sphinx
[pbr] Generating AUTHORS
[pbr] AUTHORS complete (0.0s)
Running Sphinx v1.2.3
loading pickled environment... not yet created
Using openstack theme from /home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/oslosphinx/theme
building [html]: all source files
updating environment: 9 added, 0 changed, 0 removed
[reno] scanning /home/pabelanger/git/openstack/reno/examples/notes for current branch release notes
Traceback (most recent call last):
  File "setup.py", line 29, in <module>
    pbr=True)
  File "/usr/lib64/python2.7/distutils/core.py", line 151, in setup
    dist.run_commands()
  File "/usr/lib64/python2.7/distutils/dist.py", line 953, in run_commands
    self.run_command(cmd)
  File "/usr/lib64/python2.7/distutils/dist.py", line 972, in run_command
    cmd_obj.run()
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/pbr/builddoc.py", line 198, in run
    setup_command.BuildDoc.run(self)
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/sphinx/setup_command.py", line 161, in run
    app.build(force_all=self.all_files)
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/sphinx/application.py", line 216, in build
    self.builder.build_all()
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/sphinx/builders/__init__.py", line 177, in build_all
    self.build(None, summary='all source files', method='all')
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/sphinx/builders/__init__.py", line 234, in build
    purple, length):
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/sphinx/builders/__init__.py", line 134, in status_iterator
    for item in iterable:
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/sphinx/environment.py", line 478, in update_generator
    self.read_doc(docname, app=app)
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/sphinx/environment.py", line 628, in read_doc
    pub.publish()
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/docutils/core.py", line 217, in publish
    self.settings)
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/docutils/readers/__init__.py", line 72, in read
    self.parse()
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/docutils/readers/__init__.py", line 78, in parse
    self.parser.parse(self.input, document)
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/docutils/parsers/rst/__init__.py", line 172, in parse
    self.statemachine.run(inputlines, document, inliner=self.inliner)
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/docutils/parsers/rst/states.py", line 170, in run
    input_source=document['source'])
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/docutils/statemachine.py", line 239, in run
    context, state, transitions)
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/docutils/statemachine.py", line 460, in check_line
    return method(match, context, next_state)
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/docutils/parsers/rst/states.py", line 2299, in explicit_markup
    nodelist, blank_finish = self.explicit_construct(match)
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/docutils/parsers/rst/states.py", line 2311, in explicit_construct
    return method(self, expmatch)
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/docutils/parsers/rst/states.py", line 2054, in directive
    directive_class, match, type_name, option_presets)
  File "/home/pabelanger/git/openstack/reno/.tox/docs/lib/python2.7/site-packages/docutils/parsers/rst/states.py", line 2103, in run_directive
    result = directive_instance.run()
  File "/home/pabelanger/git/openstack/reno/reno/sphinxext.py", line 58, in run
    notes = scanner.get_notes_by_version(reporoot, notesdir, branch)
  File "/home/pabelanger/git/openstack/reno/reno/scanner.py", line 161, in get_notes_by_version
    versions_by_date = _get_version_tags_on_branch(reporoot, branch)
  File "/home/pabelanger/git/openstack/reno/reno/scanner.py", line 137, in _get_version_tags_on_branch
    tag_results = utils.check_output(tag_cmd, cwd=reporoot)
  File "/home/pabelanger/git/openstack/reno/reno/utils.py", line 58, in check_output
    raise subprocess.CalledProcessError(retcode, args, output=output)
subprocess.CalledProcessError: Command '(['git', 'log', '--simplify-by-decoration', '--pretty="%d"'],)' returned non-zero exit status 128