Google Cloud storage on dev_appserver on Cloud Shell - google-app-engine

Question

I am trying to use Google Cloud Storage from GAE and all works fine when deployed. I am however unable to get the storage to work on the development server that runs on Google Cloud Shell.
I am using the cloudstorage API and my understanding it that dev_appserver should access same buckets as the deployed application. For me working with local data would be fine as well.
The development server is invoked by dev_appserver.py .
I have played around with the non-documented default_gcs_bucket_name flag but no luck.
I have set he cloud shell to work with the correct project using gcloud init. I have also tried to use the new google.cloud.storage API without luck.
The same error as referenced below is triggered if I run the sample provided here: App Engine and Google Cloud Storage Sample.
Anyone?
Edit: I get the same error regardless of whether I supply a valid or an invalid bucket name.
app.yaml
runtime: python27
api_version: 1
threadsafe: true
builtins:
- remote_api: on
handlers:
- url: /.*
script: main.app
main.py
import logging
import cloudstorage as gcs
import webapp2
from google.appengine.api import app_identity
class MainPage(webapp2.RequestHandler):
def get(self):
self.response.headers['Content-Type'] = 'text/plain'
bucket_name = "xxxx-xxxxxx.appspot.com"
stats = gcs.listbucket('/'+bucket_name)
for stat in stats:
self.response.write(repr(stat) + '')
app = webapp2.WSGIApplication([
('/', MainPage),
], debug=True)
Log
INFO 2017-06-07 20:36:42,068 devappserver2.py:116] Skipping SDK update check.
INFO 2017-06-07 20:36:42,105 api_server.py:297] Starting API server at: http://0.0.0.0:38829
INFO 2017-06-07 20:36:42,110 dispatcher.py:209] Starting module "default" running at: http://0.0.0.0:8080
INFO 2017-06-07 20:36:42,111 admin_server.py:116] Starting admin server at: http://0.0.0.0:8000
ERROR 2017-06-07 20:36:54,836 api_server.py:374] Exception while handling service_name: "app_identity_service"
method: "GetAccessToken"
request: "\n7https://www.googleapis.com/auth/devstorage.full_control"
request_id: "QBrGUwjoJT"
Traceback (most recent call last):
File "/google/google-cloud-sdk/platform/google_appengine/google/appengine/tools/devappserver2/api_server.py", line 349, in _handle_POST
api_response = _execute_request(request).Encode()
File "/google/google-cloud-sdk/platform/google_appengine/google/appengine/tools/devappserver2/api_server.py", line 225, in _execute_request
make_request()
File "/google/google-cloud-sdk/platform/google_appengine/google/appengine/tools/devappserver2/api_server.py", line 220, in make_request
request_id)
File "/google/google-cloud-sdk/platform/google_appengine/google/appengine/api/apiproxy_stub.py", line 131, in MakeSyncCall
method(request, response)
File "/google/google-cloud-sdk/platform/google_appengine/google/appengine/api/app_identity/app_identity_defaultcredentialsbased_stub.py", line 195, in _Dynamic_GetAccessToken
'expires': now + token.expires_in,
TypeError: unsupported operand type(s) for +: 'int' and 'NoneType'
WARNING 2017-06-07 20:36:54,838 tasklets.py:468] suspended generator _make_token_async(rest_api.py:55) raised RuntimeError(TypeError("unsupported operand type(s) for +: 'int' and 'NoneType'",))
WARNING 2017-06-07 20:36:54,839 tasklets.py:468] suspended generator get_token_async(rest_api.py:224) raised RuntimeError(TypeError("unsupported operand type(s) for +: 'int' and 'NoneType'",))
WARNING 2017-06-07 20:36:54,839 tasklets.py:468] suspended generator urlfetch_async(rest_api.py:259) raised RuntimeError(TypeError("unsupported operand type(s) for +: 'int' and 'NoneType'",))
WARNING 2017-06-07 20:36:54,839 tasklets.py:468] suspended generator run(api_utils.py:164) raised RuntimeError(TypeError("unsupported operand type(s) for +: 'int' and 'NoneType'",))
WARNING 2017-06-07 20:36:54,839 tasklets.py:468] suspended generator do_request_async(rest_api.py:198) raised RuntimeError(TypeError("unsupported operand type(s) for +: 'int' and 'NoneType'",))
WARNING 2017-06-07 20:36:54,839 tasklets.py:468] suspended generator do_request_async(storage_api.py:137) raised RuntimeError(TypeError("unsupported operand type(s) for +: 'int' and 'NoneType'",))

Answer 1

Follow the instructions available in How the Application Default Credentials work (condition 1.)
It involves setting GOOGLE_APPLICATION_CREDENTIALS env variable to point to a valid json credentials file.
For these tests, I just created a new one selecting App Engine default service account:
...and it worked beautifully.
According to How the Application Default Credentials work running gcloud auth application-default login (condition 2.) should also solve the issue but I have not been able to make it work on Cloud Shell, it fails with the same "access token related" error :-(

Answer 2

dev_appserver.py uses configurations set in your local environment. Make sure the configs set on gcloud init is also correct for deploying to production.
To set Cloud Storage account permissions, go to Cloud Console then:
Storage > Browser > Right Button of your bucket > Edit bucket permissions
Add your account as Storage Admin or the likes.

Answer 3

Make sure you're logged in and have authorized the default service credentials.
% gcloud auth login
% gcloud auth application-default login