You're trying to pull a bill there that has not yet been marked up by Cato. The list of completed bills is available via the API at
http://deepbills.cato.org/api/1/bills and you should limit yourself to those.
I should have a better error message in place than the 502 but regardless the result would be you're not going to get a result. I don't think it's in our interest to return a non-marked-up bill, as we don't want to be in the raw bill distribution business. So the best case would be maybe a 404 rather than an application error.