Import Error when trying to migrate Google App Engine Python 2 app using NDB to the Cloud NDB Python 3 library

I am currently starting the process of preparing an App Engine app for Python 3 migration. During the first step:

1. Migrate the App Engine bundled services in your Python 2 app to Google Cloud services ...

Following all the instructions to switch the datastore module from google.appengine.ext.ndb to google.cloud.ndb, I immediately get the following Import Error:

  File "/usr/lib/google-cloud-sdk/platform/google_appengine/google/appengine/runtime/wsgi.py", line 240, in Handle
handler = _config_handle.add_wsgi_middleware(self._LoadHandler())
  File "/usr/lib/google-cloud-sdk/platform/google_appengine/google/appengine/runtime/wsgi.py", line 311, in _LoadHandler
handler, path, err = LoadObject(self._handler)
  File "/usr/lib/google-cloud-sdk/platform/google_appengine/google/appengine/runtime/wsgi.py", line 85, in LoadObject
obj = __import__(path[0])
  File "/home/---.py", line 8, in <module>
from google.cloud import ndb
  File "/home/test_env/local/lib/python2.7/site-packages/google/cloud/ndb/__init__.py", line 28, in <module>
from google.cloud.ndb.client import Client
  File "/home/test_env/local/lib/python2.7/site-packages/google/cloud/ndb/client.py", line 23, in <module>
from google.cloud import _helpers
  File "/home/test_env/local/lib/python2.7/site-packages/google/cloud/_helpers.py", line 29, in <module>
from six.moves import http_client

ImportError: No module named moves

This happens whether or not I am testing in a virtual environment. Importing six.moves works in a python console.

Apparently this is an issue with the bundled test server dev_appserver.py. Found it solved here by Andrewsg:

I think we've identified an issue with devappserver related to the six library specifically. Could you please try a workaround? Add the line: import six; reload(six) to the top of your app, before NDB is loaded