Handle None error_cb and dr_cb

Author: edenhill

confluent_kafka/src/Producer.c

@@ -280,9 +280,9 @@ static PyObject *Producer_produce (Handle *self, PyObject *args,
 		return NULL;
 	}
 
-	if (!dr_cb)
+	if (!dr_cb || dr_cb == Py_None)
 		dr_cb = self->u.Producer.default_dr_cb;
-	if (!partitioner_cb)
+	if (!partitioner_cb || partitioner_cb == Py_None)
 		partitioner_cb = self->u.Producer.partitioner_cb;
 
 	/* Create msgstate if necessary, may return NULL if no callbacks

confluent_kafka/src/confluent_kafka.c

@@ -1113,10 +1113,14 @@ rd_kafka_conf_t *common_conf_setup (rd_kafka_type_t ktype,
 			continue;
 
 		} else if (!strcmp(k, "error_cb")) {
-			if (h->error_cb)
+			if (h->error_cb) {
 				Py_DECREF(h->error_cb);
-			h->error_cb = vo;
-			Py_INCREF(h->error_cb);
+				h->error_cb = NULL;
+			}
+			if (vo != Py_None) {
+				h->error_cb = vo;
+				Py_INCREF(h->error_cb);
+			}
 			Py_DECREF(ks);
 			continue;
 		}