Comment 1 for bug 1481560

The error msg is as follows, I see the centos source base dockerfile has git installed, so it's reasonable for ubuntu base doing the similar.
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Processing /neutron
    Complete output from command python setup.py egg_info:
    ERROR:root:Error parsing
    Traceback (most recent call last):
      File "/usr/local/lib/python2.7/dist-packages/pbr/core.py", line 109, in pbr
        attrs = util.cfg_to_args(path)
      File "/usr/local/lib/python2.7/dist-packages/pbr/util.py", line 243, in cfg_to_args
        pbr.hooks.setup_hook(config)
      File "/usr/local/lib/python2.7/dist-packages/pbr/hooks/__init__.py", line 25, in setup_hook
        metadata_config.run()
      File "/usr/local/lib/python2.7/dist-packages/pbr/hooks/base.py", line 27, in run
        self.hook()
      File "/usr/local/lib/python2.7/dist-packages/pbr/hooks/metadata.py", line 26, in hook
        self.config['name'], self.config.get('version', None))
      File "/usr/local/lib/python2.7/dist-packages/pbr/packaging.py", line 640, 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?
    error in setup command: Error parsing /tmp/pip-iXz7EF-build/setup.cfg: Exception: Versioning for this project requires either an sdist tarball, or access to an upstream git repository. Are you sure that git is installed?