That's an error message we write out in FreeCAD if the corresponding Swig interface cannot be found.
FYI: Querying the C++ internals of a Swig python module is a pain. For every minor release the API completely changes. On Debian that's normally not a problem because you have only one Swig version system-wide but on Windows e.g. you cannot rely on this. So, you need a general way to find out what the Swig version is. In FreeCAD the solution is a bit crude because we read in the generated python file and get the Swig number from there.