If they ingest a little aspen here an there they should be fine. In the wild they will ingest things there an there. I seen in one of the Sloan brothers videos of them putting sandi chips down and a paper towel down as well to stop them from ingesting the sandi chips. This would work as well for you if you dont want yours ingesting the aspen. I personally have never seen or heard of a snake ingesting paper towel or newspaper during feeding but it is very well possible they could but the likely hood of it is rare.