Deterministically shuffle identically under both py2 + py3.

def _shuffled(seq):
    """Deterministically shuffle identically under both py2 + py3."""
    fixed_random = random.Random()
    if six.PY2:  # pragma: no cover (py2)
        fixed_random.seed(FIXED_RANDOM_SEED)
    else:  # pragma: no cover (py3)
        fixed_random.seed(FIXED_RANDOM_SEED, version=1)

    seq = list(seq)
    random.shuffle(seq, random=fixed_random.random)
    return seq