ImagePsfMatchTask has no run method. This is in violation of the policy espoused in RFC-352. Worse, it means that SnapPsfMatchTask (which inherits from ImagePsfMatchTask has no run method either, and that, in turn, means that lsst.pipe.tasks.SnapCombineTask will fail when run with doDiffIm set to True:

  File "/mnt/lsst/src/lsst/pipe_tasks/python/lsst/pipe/tasks/snapCombine.py", line 210, in run

    diffRet = self.diffim.run(snap0, snap1, "subtractExposures")

AttributeError: 'SnapPsfMatchTask' object has no attribute 'run'

Note that it's clear that this is bad, but it's not clear what the correct resolution is — it may be to fix ImagePsfMatchTask, but it may also be to say that the doDiffIm option in SnapCombineTask isn't useful. That's something to discuss with product owners.