Seriously dude, you don't need a light or CHE in one of the commercial snake cages. A RHP or FW will heat it perfectly, and if you're dead set on having a light, put a fluorescent fixture in it. You can get lamps for them that are very dim to mimic moonlight, or just go with a blue LED fixture. Don't ruin the humidity and heat retaining qualities of the cage by cutting holes for light fixtures that are absolutely unnecessary.
I also mean no offense!! FYI