During rattlesnake roundups in sweetwater TX, they would spray regular gasoline from a hudson style garden sprayer into the dens or crawl spaces where the snakes could be seen lying coiled up out of reach. In just a few seconds, when the fumes would hit the snakes, they would come streaming out into open areas where they were easily gathered by the crew waiting with tongs and barrells. If you are very carful, and take reasonable safety precautions (extinguish all open flame, ignition sources, etc.), and make sure you do not spray liquid gas on your pet, then it may do the trick. Please be careful and good luck!
....Ummm..... I recommend NOT doing that!