Install Setuptools.

def _install(archive_filename, install_args=()):
    """Install Setuptools."""
    with archive_context(archive_filename):
        # installing
        log.warn('Installing Setuptools')
        if not _python_cmd('setup.py', 'install', *install_args):
            log.warn('Something went wrong during the installation.')
            log.warn('See the error message above.')
            # exitcode will be 2
            return 2