Thanks for bringing attention to this Rémi. 

I'm a bit concerned that it might be a bit late into the 3.9 beta to incorporate a removal and that we might need to consider delaying to 3.10, but I'll leave that up to Lukasz. Feel free to open a PR in the meantime since it will need to be removed either way, the only main difference is whether or not it gets backported to 3.9.

(I elevated the priority to "release blocker", as I think it should be a blocker for 3.10 if it's not for 3.9. The version should be updated accordingly.)