Hey Steve,
It's not uncommon to pass some blood when they shed. I wouldn't worry about it. If your concerned about constipation than you can soak him in 85 degree water for a bit to see if it helps him pass it. But you really don't have anything to worry about. Some of my ball pythons defecate once every two or 3 weeks, and others go less frequently. I think your main concern was the blood and I don't think it should be an issue. If the bleeding continues or intensifies I would bring him to a vet but blood on the cloaca or on the substrate after a shed is not uncommon by any means.
Hope this helped
Chris.