Well, any snake can take a crap on your, so I presume you are refering to musking? I don't believe rattlers musk, but I'm not sure.
Since you are thinking colubrid, here is a pic of a sonoran gopher
Does it have big dark patches right behind its head? If so it could be a texas night snake. Also, many colubrids imitate rattler behaviour (especially in regions where there are lots of rattlers) as a defense mechanism, which would explain the tail threats.