Well maybe you could sit down with him, and talk to him about how you feel about the snake. Perhaps he knows someone who could watch it for him, but also perhaps bring up the subject of how afraid you are of them and if he really can't find anywhere else, he can maybe bring the snake and leave it somewhere where you won't even have to see it. If you have a room you are letting him use tell him you just need to not ever see it, please keep it in the room at all times and safely contained. Of course you'll have to do what you feel right about, but I would just talk it over with him, and maybe you guys can work something out that will work for both of you. If he is going to be there for only two weeks or so, the snake wouldn't even need to eat in that time and could be fed later once he moves again. Good luck, hope you can work something out.