So after the whole kerfluffle over what Pope said this or didn't say it, we realized that in all truth, it does not matter.
You and I know All Pets do Go to Heaven. no attribution needed. So we revised the shirt, and just removed the "byline."

The new shirt comes in two options - a normal, and a women's fitted T-shirt, and the hoodie is also available!
Here's the link: http://teespring.com/petheaven