Travis has some aliases set up for Rubinius that are basically broken. In this case `rbx` is causing RVM to try to run rubinius-2.0.0-weekly20130922-d18 (ie a weekly build from Sept 22nd, see https://travis-ci.org/engineyard/todo/jobs/12914260)

I'd recommend removing `rbx-18mode`, `rbx-19mode`, and `rbx` and using `rbx-2.1.1` instead. Instead of tracking Rubinius head, every so often update to the latest Rubinius release. Alternatively, we could try to convince Travis to make `rbx` reference the latest release, but that essentially means getting RVM to do that and that's a battle I'm not interested in. :)