The changes on this ticket have made it necessary to guard calls to lsst.afw.display.ds9.Buffering() with (e.g.) if display; that seems to have previously been a harmless no-op when no display is active. I'm fixing all code that called it unguarded on DM-8002 (I think that's a good idea in all of the cases I've found regardless), but if it is an undesirable change it should either be fixed here or a new ticket opened for it.

Robert Lupton — I believe this work has hit master (albeit without a merge commit). Can you confirm &, if appropriate, close the ticket? Thanks.

See note on merge-woes in DM-7869

@rhl, apologies for never reviewing this ticket.