So Where's the Antipope?

[StupidAlarmClockGuy]

In my Late Era game as France, I've seen the HRE get excommunicated three or four times so far. They've got plenty of +5 piety bishops from denouncing heretics over and over, but not one of them has claimed the title of Antipope yet. It's turn 50. Is there something else from looking over the campaign script that I missed? Because there's no antipope anywhere on the map yet.

[Ferdiad]

I get them as the player easily, not so sure about AI.