Added unit-test for error_cb

tests/test_KafkaError.py

@@ -0,0 +1,30 @@
+#!/usr/bin/env python
+
+from confluent_kafka import Producer, KafkaError, KafkaException
+import time
+
+seen_all_brokers_down = False
+
+def error_cb (err):
+    print('error_cb', err)
+    if err.code() == KafkaError._ALL_BROKERS_DOWN:
+        global seen_all_brokers_down
+        seen_all_brokers_down = True
+
+
+def test_error_cb():
+    """ Test the error callback. """
+
+    global seen_all_brokers_down
+
+    # Configure an invalid broker and make sure the ALL_BROKERS_DOWN
+    # error is seen in the error callback.
+    p = Producer({'bootstrap.servers': '127.0.0.1:1', 'socket.timeout.ms':10,
+                  'error_cb': error_cb})
+
+    t_end = time.time() + 5
+
+    while not seen_all_brokers_down and time.time() < t_end:
+        p.poll(1)
+
+    assert seen_all_brokers_down