Address review comments

Change-Id: I957fa992850ed3305dbcad5cd73ed61a7eedb63c

Author: Jon Wayne Parrott

bigquery/cloud-client/snippets.py

@@ -66,6 +66,7 @@ def list_tables(dataset_name, project=None):
 
     if not dataset.exists():
         print('Dataset {} does not exist.'.format(dataset_name))
+        return
 
     tables = []
     page_token = None
@@ -95,6 +96,7 @@ def list_rows(dataset_name, table_name, project=None):
 
     if not table.exists():
         print('Table {}:{} does not exist.'.format(dataset_name, table_name))
+        return
 
     # Reload the table so that the schema is available.
     table.reload()

bigquery/cloud-client/snippets_test.py

@@ -1,9 +1,10 @@
-# Copyright 2015, Google, Inc.
+# Copyright 2016 Google Inc. All Rights Reserved.
+#
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
-#    http://www.apache.org/licenses/LICENSE-2.0
+#     http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,