BigQuery: Add Data Transfer Service quickstart. [(#1295)](GoogleCloud…

…Platform/python-docs-samples#1295)

* BigQuery: Add Data Transfer Service quickstart.

Client library docs:
https://googlecloudplatform.github.io/google-cloud-python/latest/bigquery_datatransfer/index.html

* Enable BigQuery Data Transfer API in test project.
* Remove project from quickstart test assertion. Don't depend on specific data sources being available.

I believe the reason the tests are failing is that the data sources
weren't allowed for the test project because the API was enabled, but
the project wasn't enrolled as described in
https://cloud.google.com/bigquery/docs/enable-transfer-service

samples/snippets/quickstart.py

@@ -0,0 +1,41 @@
+#!/usr/bin/env python
+
+# Copyright 2017 Google LLC
+#
+# 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
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+def run_quickstart():
+    # [START bigquery_datatransfer_quickstart]
+    from google.cloud import bigquery_datatransfer
+
+    client = bigquery_datatransfer.DataTransferServiceClient()
+
+    project = 'my-project'  # TODO: Update to your project ID.
+
+    # Get the full path to your project.
+    parent = client.project_path(project)
+
+    print('Supported Data Sources:')
+
+    # Iterate over all possible data sources.
+    for data_source in client.list_data_sources(parent):
+        print('{}:'.format(data_source.display_name))
+        print('\tID: {}'.format(data_source.data_source_id))
+        print('\tFull path: {}'.format(data_source.name))
+        print('\tDescription: {}'.format(data_source.description))
+    # [END bigquery_datatransfer_quickstart]
+
+
+if __name__ == '__main__':
+    run_quickstart()

samples/snippets/quickstart_test.py

@@ -0,0 +1,41 @@
+# Copyright 2017 Google LLC
+#
+# 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
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import os
+
+import mock
+import pytest
+
+import quickstart
+
+
+PROJECT = os.environ['GCLOUD_PROJECT']
+
+
+@pytest.fixture
+def mock_project_path():
+    """Mock out project and replace with project from environment."""
+    project_patch = mock.patch(
+        'google.cloud.bigquery_datatransfer.DataTransferServiceClient.'
+        'project_path')
+
+    with project_patch as project_mock:
+        project_mock.return_value = 'projects/{}'.format(PROJECT)
+        yield project_mock
+
+
+def test_quickstart(capsys, mock_project_path):
+    quickstart.run_quickstart()
+    out, _ = capsys.readouterr()
+    assert 'Supported Data Sources:' in out

samples/snippets/requirements.txt

@@ -0,0 +1 @@
+google-cloud-bigquery-datatransfer==0.1.0