Ensure that quickstart examples actually work. (#4398)

Closes #4394.

pubsub/README.rst

@@ -66,12 +66,12 @@ messages to it
     from google.cloud import pubsub
 
     publisher = pubsub.PublisherClient()
-    topic = 'projects/{project_id}/topics/{topic}'.format(
+    topic_name = 'projects/{project_id}/topics/{topic}'.format(
         project_id=os.getenv('GOOGLE_CLOUD_PROJECT'),
         topic='MY_TOPIC_NAME',  # Set this to something appropriate.
     )
-    publisher.create_topic()
-    publisher.publish(topic, b'My first message!', spam='eggs')
+    publisher.create_topic(topic_name)
+    publisher.publish(topic_name, b'My first message!', spam='eggs')
 
 To learn more, consult the `publishing documentation`_.
 
@@ -90,15 +90,16 @@ the topic, and subscribe to that.
     from google.cloud import pubsub
 
     subscriber = pubsub.SubscriberClient()
-    topic = 'projects/{project_id}/topics/{topic}'.format(
+    topic_name = 'projects/{project_id}/topics/{topic}'.format(
         project_id=os.getenv('GOOGLE_CLOUD_PROJECT'),
         topic='MY_TOPIC_NAME',  # Set this to something appropriate.
     )
     subscription_name = 'projects/{project_id}/subscriptions/{sub}'.format(
         project_id=os.getenv('GOOGLE_CLOUD_PROJECT'),
         sub='MY_SUBSCRIPTION_NAME',  # Set this to something appropriate.
     )
-    subscription = subscriber.create_subscription(topic, subscription)
+    subscription = subscriber.create_subscription(
+        name=subscription_name, topic=topic_name)
 
 The subscription is opened asychronously, and messages are processed by
 use of a callback.