369 static PyObject *
370 urj_pyc_shift_dr (urj_pychain_t *self)
371 {
372     urj_chain_t *urc = self->urchain;
373     if (!urj_pyc_precheck (urc, UPRC_CBL))
when considering value == (int)0 from chain.c:373
taking True path
374         return NULL;
375 
376     /*  TODO: need a way to not capture the TDO output
377      */
378     return urj_py_chkret (urj_tap_chain_shift_data_registers (urc, 1));
379 }
returning (PyObject*)NULL without setting an exception