Update changelog and handle review comments

CHANGELOG.md

@@ -1,5 +1,18 @@
 # Confluent's Python client for Apache Kafka
 
+## v1.8.0
+
+v1.8.0 is a maintenance release with the following fixes and enhancements:
+
+### Enhancements
+
+- Support rd_kafka_memberid() from python clients (#1154).
+
+confluent-kafka-python is based on librdkafka v1.8.0, see the
+[librdkafka release notes](https://github.com/edenhill/librdkafka/releases/tag/v1.8.0)
+for a complete list of changes, enhancements, fixes and upgrade considerations.
+
+
 ## v1.7.0
 
 v1.7.0 is a maintenance release with the following fixes and enhancements:

src/confluent_kafka/src/Consumer.c

@@ -993,10 +993,10 @@ static PyObject *Consumer_memberid (Handle *self, PyObject *args,
         memberid = rd_kafka_memberid(self->rk);
 
         if (!memberid)
-                return NULL;
+                Py_RETURN_NONE;
 
         memberidobj = Py_BuildValue("s", memberid);
-        rd_kafka_mem_free(NULL, memberid);
+        rd_kafka_mem_free(self->rk, memberid);
 
         return memberidobj;
 }

tests/integration/consumer/test_consumer_memberid.py

@@ -30,11 +30,13 @@ def test_consumer_memberid(kafka_cluster):
     consumer = kafka_cluster.consumer(consumer_conf)
 
     assert consumer is not None
+    assert len(consumer.memberid()) == 0
     kafka_cluster.seed_topic(topic, value_source=[b'memberid'])
 
     consumer.subscribe([topic])
     msg = consumer.poll(10)
     assert msg is not None
     assert msg.value() == b'memberid'
     assert len(consumer.memberid()) > 0
+    assert isinstance(consumer.memberid(), str) is True
     consumer.close()