Convert remaining KafkaConsumer tests to pytest (#1886)

This makes it so the only remaining use of `unittest` is in the old
tests of the deprecated `Simple*` clients. All `KafkaConsumer` tests are
migrated to `pytest`.

I also had to bump the test iterations up on one of the tests, I think there was a race condition there that was more commonly hit under pytest , planning to cleanup that in a followup PR. See #1886 (comment) for details.

test/conftest.py

@@ -1,5 +1,7 @@
 from __future__ import absolute_import
 
+import uuid
+
 import pytest
 
 from test.testutil import env_kafka_version, random_string
@@ -137,3 +139,27 @@ def _set_conn_state(state):
     conn.connected = lambda: conn.state is ConnectionStates.CONNECTED
     conn.disconnected = lambda: conn.state is ConnectionStates.DISCONNECTED
     return conn
+
+
+@pytest.fixture()
+def send_messages(topic, kafka_producer, request):
+    """A factory that returns a send_messages function with a pre-populated
+    topic topic / producer."""
+
+    def _send_messages(number_range, partition=0, topic=topic, producer=kafka_producer, request=request):
+        """
+            messages is typically `range(0,100)`
+            partition is an int
+        """
+        messages_and_futures = []  # [(message, produce_future),]
+        for i in number_range:
+            # request.node.name provides the test name (including parametrized values)
+            encoded_msg = '{}-{}-{}'.format(i, request.node.name, uuid.uuid4()).encode('utf-8')
+            future = kafka_producer.send(topic, value=encoded_msg, partition=partition)
+            messages_and_futures.append((encoded_msg, future))
+        kafka_producer.flush()
+        for (msg, f) in messages_and_futures:
+            assert f.succeeded()
+        return [msg for (msg, f) in messages_and_futures]
+
+    return _send_messages

test/test_consumer_group.py

@@ -29,6 +29,7 @@ def test_consumer(kafka_broker, topic):
     assert consumer._client._conns[node_id].state is ConnectionStates.CONNECTED
     consumer.close()
 
+
 @pytest.mark.skipif(not env_kafka_version(), reason="No KAFKA_VERSION set")
 def test_consumer_topics(kafka_broker, topic):
     consumer = KafkaConsumer(bootstrap_servers=get_connect_str(kafka_broker))
@@ -38,6 +39,7 @@ def test_consumer_topics(kafka_broker, topic):
     assert len(consumer.partitions_for_topic(topic)) > 0
     consumer.close()
 
+
 @pytest.mark.skipif(env_kafka_version() < (0, 9), reason='Unsupported Kafka Version')
 def test_group(kafka_broker, topic):
     num_partitions = 4