Would it be possible to create a new constraint "type" with python? Obviously it is possible to add new mesh "type" with python in the list of create mesh. I think I read that it isn't possible to create a new "modifier" type with python. What about constraints type (like a 4th kind of "track to" for example)? Would this be possible to do in python and if yes where should I start to look at in the docs ?

Thx a lot,
Stan

Almost three years after ..., I was wondering if that is still the case ? Are we able to create new modifiers or constraints types with the python API in 2.78 ?
Currently we don't support Python constraints (though they were supported at one point in Blender 2.4x).