When using a MongoDB URL containing a database name and no password, PyMongo outputs: "UserWarning: database name or authSource in URI is being ignored. If you wish to authenticate to goji, you must provide a username and password."

This assumes that PyMongo is the only consumer of the MongoDB URL, which is often not the case. (Our codebase extracts the database name from the URL.)

Working around this is ugly (eg. generating different URLs) and the warning is spammy when using multiprocessing.Pool. The authSource part might make sense, since it's probably meaningless without a password, but please remove the warning about ignoring the database name.