Warner bros Threaten to sue some guy for giving a Harry Potter themed birthday party. What do you thing when they heard an unlicensed game of their property has been sold. And for making games, they are only selling rights to highest bidder like Lego. So I don't think they will give rights to an indie developers.
Here is a newsletter about one of their threats
https://www.theguardian.com/film/2018/jun/16/harry-potter-warner-bros-wizard-fan...
And another
https://www.mirror.co.uk/news/uk-news/film-giant-warner-bros-threatens-11576262