lscsoft-decommissioned
As discussed in https://sympa.ligo.org/wws/arc/daswg/2019-08/msg00086.html create a new lscsoft-decommissioned metapackage that lists decommissioned packages as Conflicts to avoid leaving legacy packages installed only to discover that someone is still using them a long time later. For example, I believe glue-segments, skyarea and seaborn have been decommissioned (though it DASWG query is pending for any remaining users of seboarn after LALInference-1.11.0 dropped that dependency).