Add the Pub/Sub handle_publisher_error sample [(#1440)](GoogleCloudPlatform/python-docs-samples#1440)

* Add the Pub/Sub handle_publisher_error sample

* Update requirements.txt

* Update publisher.py

* Update publisher.py

* Added region tag

Author: chenyumic

samples/snippets/publisher.py

@@ -22,6 +22,7 @@
 """
 
 import argparse
+import concurrent.futures
 
 from google.cloud import pubsub_v1
 
@@ -123,6 +124,38 @@ def publish_messages_with_futures(project, topic_name):
     # [END pubsub_publisher_concurrency_control]
 
 
+def publish_messages_with_error_handler(project, topic_name):
+    """Publishes multiple messages to a Pub/Sub topic with an error handler."""
+    # [START pubsub_publish_messages_error_handler]
+    publisher = pubsub_v1.PublisherClient()
+    topic_path = publisher.topic_path(project, topic_name)
+
+    # When you publish a message, the client returns a Future. This Future
+    # can be used to track if an error has occurred.
+    futures = []
+
+    def callback(f):
+        exc = f.exception()
+        if exc:
+            print('Publishing message on {} threw an Exception {}.'.format(
+                topic_name, exc))
+
+    for n in range(1, 10):
+        data = u'Message number {}'.format(n)
+        # Data must be a bytestring
+        data = data.encode('utf-8')
+        message_future = publisher.publish(topic_path, data=data)
+        message_future.add_done_callback(callback)
+        futures.append(message_future)
+
+    # We must keep the main thread from exiting to allow it to process
+    # messages in the background.
+    concurrent.futures.wait(futures)
+
+    print('Published messages.')
+    # [END pubsub_publish_messages_error_handler]
+
+
 def publish_messages_with_batch_settings(project, topic_name):
     """Publishes multiple messages to a Pub/Sub topic with batch settings."""
     # [START pubsub_publisher_batch_settings]

samples/snippets/requirements.txt

@@ -1 +1,2 @@
 google-cloud-pubsub==0.32.1
+futures==3.1.1; python_version < '3'