Lint treats unknown warning attributes as an error #2480
Description
Right now, lint will raise an error if it sees a warning attribute that it doesn't recognize. This is annoying because it means that a snapshot is required in order to introduce a new lint setting and then add suppressions for it.
The right thing to do is to instead use the lint warning settings to configure what lint does when it doesn't recognize a warning attribute. Need to pick a default, though. (Probably warning?)