Jasig/uPortal — pull request #320 by apetro (2014-05-13 11:03:23+00:00)
Title: Trivial: fix null arg validation message.

Make `principalFromUser` `null` validation failure not-Marketplace-specific.

Credit to @drewwills for catching this in https://github.com/Jasig/uPortal/commit/e974b1ea294653ca7b67aa9b39a021e1e3ab5fb1#commitcomment-6295316 .