IMO just updating the documentation would not be enough.

I suggest wrapping sys.setrecursionlimit() and *adding* 30 to the given limit, to offset the call stack depth added by IDLE. This makes more sense to me than max(n, 50), which I imagine would cause a lot of confusion in cases where it comes into effect.

If that's not acceptable, then I suggest wrapping it to raise an informative exception if the given limit is too low.