sounds very bad. sounds really like some nasty mites. If they like to be under the scales of snakes, they are bloodsuckers.

You need to visit a vet ASAP. I guess it will be a medication that is (more or less) harmless for the python but deadly for the mites, or the whole surface of the snake gets treated with something. And at the same time all substrate and everything needs to be replaced or cleaned to the point of being sterile. Good luck! But this time, i think, this forum cannot replace a veterinarian. Consider anything i said merely as hints, except that you really need a professional now.