Script to rolling-start Nomulus (#888)

* Script to rolling-start Nomulus

Add a script to restart Nomulus non-disruptively. This can be used after
a configuration change to external resources (e.g.,  Cloud SQL
credential) to make Nomulus pick up the latest config.

Also added proper support to paging based List api methods, replacing the
current hack that forces the server to return everything in one response.
The List method for instances has a lower limit on page size than others
which is not sufficient for our project.

release/rollback/appengine_test.py

@@ -17,11 +17,14 @@ import unittest
 from unittest import mock
 from unittest.mock import patch
 
+from googleapiclient import http
+
 import appengine
 import common
 
 
-def setup_appengine_admin() -> Tuple[object, object]:
+def setup_appengine_admin(
+) -> Tuple[appengine.AppEngineAdmin, http.HttpRequest]:
     """Helper for setting up a mocked AppEngineAdmin instance.
 
     Returns:
@@ -32,7 +35,7 @@ def setup_appengine_admin() -> Tuple[object, object]:
     # Assign mocked API response to mock_request.execute.
     mock_request = mock.MagicMock()
     mock_request.uri.return_value = 'myuri'
-    # Mocked resource shared by services, versions, and operations.
+    # Mocked resource shared by services, versions, instances, and operations.
     resource = mock.MagicMock()
     resource.list.return_value = mock_request
     resource.get.return_value = mock_request
@@ -41,6 +44,7 @@ def setup_appengine_admin() -> Tuple[object, object]:
     apps = mock.MagicMock()
     apps.services.return_value = resource
     resource.versions.return_value = resource
+    resource.instances.return_value = resource
     apps.operations.return_value = resource
     service_lookup = mock.MagicMock()
     service_lookup.apps.return_value = apps
@@ -66,11 +70,6 @@ class AppEngineTestCase(unittest.TestCase):
         else:
             self._mock_request.execute.return_value = responses
 
-    def test_checked_request_multipage_raises(self) -> None:
-        self._set_mocked_response({'nextPageToken': ''})
-        self.assertRaises(appengine.PagingError,
-                          self._client.get_serving_versions)
-
     def test_get_serving_versions(self) -> None:
         self._set_mocked_response({
             'services': [{