Run final model selection from n=2 and n=3 options.

def _select_model(n2_bounds, n2_result, n3_result, out_dir, data):
    """Run final model selection from n=2 and n=3 options.
    """
    n2_out_file = n2_result.replace(".n2.results", ".BEST.results")
    n3_out_file = n3_result.replace(".n3.results", ".BEST.results")
    if not utils.file_exists(n2_out_file) and not utils.file_exists(n3_out_file):
        cmd = _get_cmd("ModelSelection.py") + [n2_bounds, n2_result, n3_result]
        do.run(cmd, "Select best THetA model")
    if utils.file_exists(n2_out_file):
        return n2_out_file
    else:
        assert utils.file_exists(n3_out_file)
        return n3_out_file