John Swinbank has noted that obs_base tests depend on a private butler config test file in DAF_BUTLER_DIR/tests/config. Those configs are not meant to be used outside of daf_butler since they contain unexpected formatters and storage classes designed specifically for internal daf_butler tests. obs_base should not be relying on those configurations. It should be sufficient for obs_base to use a default configuration made by Butler.makeRepo.

I'm not entirely sure whether I should fix this or whether this should be handled by science pipelines.