I don't know what the settings catalog is. I think I added this line because when I ran the code under test from the spec examples without this, it didn't seem to be paying attention to the assignments I had made to `Puppet[:digest_algorithm]`. I believe I saw `Puppet.settings.use` used somewhere else in the code and assumed that it meant, "pay attention to this hunk of the settings from puppet.conf as defined in `puppet/defaults.rb`." Sounds like I was wrong.