At the moment, sims_catalogs_measures and sims_photUtils are dependent on each other. The result is an infinite loop during the 'lsst-build prepare' step:
This type of error doesn't happen every day but it has happened a number of times in the past. The build would have terminated by itself at the failsafe timeout which is currently set at 4.5 hours. However, I would prefer that it be caught and an exception returned to buildbot.