Update pytest fixtures to new yield syntax (#919)

test/conftest.py

@@ -18,10 +18,8 @@ def version():
 def zookeeper(version, request):
     assert version
     zk = ZookeeperFixture.instance()
-    def fin():
-        zk.close()
-    request.addfinalizer(fin)
-    return zk
+    yield zk
+    zk.close()
 
 
 @pytest.fixture(scope="module")
@@ -29,10 +27,8 @@ def kafka_broker(version, zookeeper, request):
     assert version
     k = KafkaFixture.instance(0, zookeeper.host, zookeeper.port,
                               partitions=4)
-    def fin():
-        k.close()
-    request.addfinalizer(fin)
-    return k
+    yield k
+    k.close()
 
 
 @pytest.fixture

test/test_metrics.py

@@ -32,8 +32,8 @@ def reporter():
 @pytest.fixture
 def metrics(request, config, reporter):
     metrics = Metrics(config, [reporter], enable_expiration=True)
-    request.addfinalizer(lambda: metrics.close())
-    return metrics
+    yield metrics
+    metrics.close()
 
 
 def test_MetricName():