The anti-impotence rule is that if a man is impotent, he isn't allowed to get married in the RCC. Which is every bit as stupid as this. Actually,
here. This has a list of all the rules that can invalidate a marriage in the Catholic Church. Infertility isn't. On the other hand, if you
can have children, but don't intend to, that does invalidate the marriage.
As for this being from the Onion, this is more like something out of a Chick Tract. That is, it's someone making things up to try and and discredit the Catholic Church. Why they bothered with all the actual ammo available, I couldn't say.