Fix description added.

Author: smurav

Python/instrumentation.c

@@ -2558,7 +2558,9 @@ PyObject *_Py_CreateMonitoringObject(void)
     err = PyObject_SetAttrString(events, "NO_EVENTS", _PyLong_GetZero());
     if (err) goto error;
     PyObject *val = PyLong_FromLong(PY_MONITORING_DEBUGGER_ID);
-    assert(val != NULL);
+    assert(val != NULL); /* Regression test for PyLong_FromLong which can return
+                            NULL in the general case. But now it can't return 
+                            NULL for arguments of small int type. */
     err = PyObject_SetAttrString(mod, "DEBUGGER_ID", val);
     Py_DECREF(val);
     if (err) goto error;