A girl in my office says that a black snake urinated on her while she was trying to get it out of her yard and that it smells like skunk. I've never heard such and can't find anything about it.
As any snake-charmer will tell you, snakes are famous for having smelly urine. They don't have urine bladders, so can't store up the urine in the way mammals can. Instead it passes into the cloacal, a common chamber and outlet for the urine, digestive, and genital passages.
grass snakes often take on a black colour but don't worry they are harmless uness you are a frog or other small creature (we have several on our land!!)