I think this is your best bet if you can't empty the house. In my area, empty houses sell quick. It is unlikely that having any pets in large numbers are going to be looked on favorably by buyers. I know if someone had a rat colony in their house I would not buy it. Too large a chance one has gotten loose and it can cost thousands to get rid of rat damage. Whether we like it or not, most people do not like snakes, so they either need to be gone or hidden if you expect to sell quickly.