Copying BaseCatalogTable objects is unreliable

[taldcroft]

These tests fail, so beware that even deepcopy is not doing what you think. Workaround is pickle.loads(pickle.dumps(aca)). I'm surprised that deepcopy() doesn't work since I thought that actually used the pickle __setstate__ and __getstate__ methods.

    aca = get_aca_catalog(**KWARGS_48464)

    aca2 = aca.__class__(aca)  # default is copy=True
    assert aca2.acqs is not aca.acqs
    for probs in aca2.acqs.cand_acqs['probs']:
        assert probs.acqs() is aca2.acqs

    aca3 = deepcopy(aca)
    for probs in aca3.acqs.cand_acqs['probs']:
        assert probs.acqs() is aca3.acqs

I'd like to fix this but initial attempts fell short. The issue revolves around the weakref in the AcqProb objects in the cand_acqs table. This is all a bit fragile and should be reworked, but not for 4.4 since it would be a big change.

However, this does work:

    acar = ACAReviewTable(aca)

    assert aca.guides is not acar.guides
    assert aca.acqs is not acar.acqs

    del aca
    gc.collect()

    # Make sure object is self-consistent and self-contained.
    for probs in acar.acqs.cand_acqs['probs']:
        assert probs.acqs() is acar.acqs