[CLIENT-3106] Fix reference count error caused by not properly increm…

…enting reference count for Py_None object (#672)

src/main/exception.c

@@ -321,6 +321,7 @@ PyObject *AerospikeException_New(void)
 
         PyObject *py_code = NULL;
         if (exception_def.code == NO_ERROR_CODE) {
+            Py_INCREF(Py_None);
             py_code = Py_None;
         }
         else {