def _shell_join(seq):
    result = []
    for word in seq:
        if isinstance(word, (tuple, MutableSequence)):
            word = _shell_join(word)
        escaped = shell_quote(word)
        result.append(escaped)
    return ' '.join(result)
`$ rio warp --dst-crs ''` used to perform a falsey check that would treat
dataset/ETHPy150Open ClusterHQ/flocker/flocker/provision/_ssh/_model.py/_shell_join--crossover with--dataset/ETHPy150Open mapbox/rasterio/tests/test_rio_warp.py/test_warp_dst_crs_empty_string