def addl_env_args(addl_env):
    """Build arguments for adding additional environment vars with env"""

    # NOTE (twilson) If using rootwrap, an EnvFilter should be set up for the
    # command instead of a CommandFilter.
    if addl_env is None:
        return []
    return ['env'] + ['%s=%s' % pair for pair in addl_env.items()]