The casting of a black actor for a character that is canonically not black. Similar to the term whitewashing, except it is for some reason socially acceptable when a black person does it.
Come on! Hermione's black now? Why does hollywood keep blackwashing like this?
Well, technically it was never expressly stated that she's canonically white.
But... She was white in all of the movies. What type of weak ass loophole is that?