I increased indent to 4 spaces and made it easier to change.

I believe old-styles classes do not have .__new__, so test of TextWrapper will ensure that they work.

Inspect.signature should have correct logic to handle .__new__, with or without .__init__. (I presume that if both are present, they must be consistent, so .__init__ should be used.) You might want to check both behavior and test file for .signature.

Idle gets .signature upgrades for free when we switch, which I hope can be in a few months at worst. Programmer use of .__new__ without .__init__ is rare enough (extremely so) that I prefer to wait. As it is, switching will already mean removing some of the current logic.