python string conversion

- use _PyUnicode_AsStringAndSize where possible
- use %R for PyErr_Format(...) rather then running repr on the object explicitly 
- use const char

source/gameengine/Ketsji/KX_PythonInit.cpp

@@ -705,7 +705,7 @@ static PyObject *gLibNew(PyObject*, PyObject* args)
 	KX_Scene *kx_scene= gp_KetsjiScene;
 	char *path;
 	char *group;
-	char *name;
+	const char *name;
 	PyObject *names;
 	int idcode;