Eh, it could also be you're handling her at the wrong time - either after a large meal that she has sausage butt from, or whenever she just feels swelled and needs to urinate. Out of my 10 retics, most will urinate every couple of days, leaving the cage pretty stout, just watch the tail end of the snake before you pull her out and make sure its not swollen, if it is, and you need to handle her, let her soak in a little bit of warm (82-86 degrees) water, and she should release the urine before your handling session begins. I've been covered in feces a couple different times, and they've had sausage butt on all occassions, but I've needed to change substrate due to floods of urine. . . each time could've been avoided had I just placed them in a holding tub, or shower while I did the cleaning. Either way, I'm usualy happy when its on me and not in the cage and I can simply change and wash my clothes versus recleaning a cage ;-)
As far as it being a defense - while this is VERY true when dealing with smaller colubrids, and even some vipers (more musking in cases of Agkistrodon) it is not likely the case with many python species. Retics, simply put, pee a lot . . . its part of their game and its just something you will encounter as they eat more and grow more.
Cheers,