implement true divide handler of the number protocol for Quantity

src/Base/UnitPyImp.cpp

@@ -194,13 +194,11 @@ int UnitPy::setCustomAttributes(const char* /*attr*/, PyObject* /*obj*/)
     return 0; 
 }
 
-#if PY_MAJOR_VERSION < 3
 PyObject * UnitPy::number_divide_handler (PyObject* /*self*/, PyObject* /*other*/)
 {
     PyErr_SetString(PyExc_NotImplementedError, "Not implemented");
     return 0;
 }
-#endif
 
 PyObject * UnitPy::number_remainder_handler (PyObject* /*self*/, PyObject* /*other*/)
 {