Calling lsst.daf.butler.Registry.queryCollections with the name of a collection that is not present raises MissingCollectionError. From the documentation, I expect it to return an iterator over an empty iterable instead.

Minimal example:

from lsst.daf.butler import Butler

butler = Butler(Butler.makeRepo("foo"))

list(butler.registry.queryCollections("collected"))

The same behavior occurs when passing ["collected"]. Passing re.compile("collected") returns an empty iterator, as expected. I have not tested a tuple or a mapping, since I'm not sure how to construct a valid example.