bloodsteel bitterraven

That was my first thought too when I read the chapter. But I was under the impression that Cersei's trial was supposed to take place before Margaery. I'm guessing what happened was that once Kevan was dead Mace said we're putting an end to this farce, and orders Tommen to give Margaery a royal pardon (and possibly Cersei too, since Tommen's rule depends on Cersei's innocence). That will of course strain the relationship between the Tyrells and the Septon. And with Cersei free and Kevan dead, she will no doubt try to mess things up again.