Dominique Boutigny also add some work on color terms to the above ticket, but that is going to be more complicated to merge (we now have reference S/N selectors thanks to Paul Price, which I'd rather use). I'll move that work to a different ticket, to make the review easier.

I've got Pierre Astier's outlier rejection and error freezing changes in this ticket branch and the test metrics updated to match (though I should add a test specifically for photometryModel.freezeErrorScales) and I'm now reprocessing HSC PDR1 on that branch. Just using the outlier rejection fix got a lot more of the HSC photometry fitting to work, so that's a good start.

Fred Moolekamp: are you able to review this? It's about +200/-90, mostly C++.

I'm curious what you think of my method of dealing with the base class logging namespace issue (i.e., getting the baseclass methods to log to the subclass logging namespace). I don't know if there's a preferred approach.

Jenkins run: https://ci.lsst.codes/blue/organizations/jenkins/stack-os-matrix/detail/stack-os-matrix/27197/pipeline

Looks good. See minor comments in PR.

New Jenkins run: https://ci.lsst.codes/job/stack-os-matrix/27217/

New new jenkins run (forgot to update one chi2 value): https://ci.lsst.codes/job/stack-os-matrix/27219/

Thanks for the review comments: you helped me find and fix a bug!

Squashed, merged, and done.