So who is Pappy Pariah and why is Sean Penn saying all those nice things about him? Little or no light was shined on the not particularly difficult mystery Friday when the actor appeared on HBO’s Real Time With Bill Maher. The guest spot was the two-time Oscar-winner’s second Pappy plug this week – he appeared Tuesday on The Late Show With Stephen Colbert – to promote the oddly-named author’s “mem-noir” Bob Honey Who Just Do Stuff. Penn narrates a free audiobook of the…