Yes, that would be the film version in question. Mr. Hochhuth told me the rather entertaining backstory of Carlo Ponti buying the film rights way back in the 60s, and then revealing he didn't actually intend to film it at all - he bought them to keep it unfilmed, so the Vatican would go easy on his union with Sophia Loren. Of course after a few years the rights went back to Hochhuth's publisher, but according to R.H. Ponti figured by then nobody would be interested in an old play anymore.
Which they weren't, until it was Costa-Gravas to the rescue.

No, I have no idea whether he was kidding me. But it is a good story.*g*