Carelessness in the merge of DM-12882 led to a failing unit test. Fixing it now.
Bug fixed, and I fixed some linting errors as requested on the PR for DM-12882. I steered clear of any cleanups that had a potential to change behavior, but happily it was mostly whitespace.
PR is here: https://github.com/lsst/meas_mosaic/pull/24
It looks great to me. Also the test passes on my Mac. Thanks for the quick fix!