Google Cloud authorization keeps failing with Python 3 - Type is None, expected one of ('authorized_user', 'service_acco

Does that help You need to add the appengine service account as having write permissions.
You can find the service account email under the "Application Settings" of the appengine console, under "Service Account Name".

I hope this helps . The JSON file that you provided is for an OAuth client. When you using application default credentials, you need to provide a JSON service account key. Try going to this page, clicking "Create service account", filling out the form, and choosing "Furnish a new private key."

around this issue You typically wouldn't use Google Cloud Pub/Sub in the client in the type of setup you describe. Cloud Pub/Sub isn't designed to scale to a number of subscriptions that are on the order of number of phones. Instead, you'd want to use Firebase Cloud Messaging. Firebase has a model that handles registration of devices to receive messages that is more in line with what you are thinking of, e.g., Set Up a Firebase Cloud Messaging Client App on Android and Implementing a Firebase Cloud Messaging Client on Chrome
What you may use Cloud Pub/Sub for is communication between different services. For example, perhaps the service that handles blog posts publishes messages on a Cloud Pub/Sub topic that your notification service subscribes to. The notification service would process the message and send out Firebase Cloud Messaging messages to end users as appropriate.

I hope this helps . The google-cloud-bigquery library is not a GAE-supplied one for the standards env, so you need to vendor it into your application (GAE doesn't care if it's installed into your local python installation). Your traceback indicates it's coming from the local installation, note the py27\lib\site-packages\google\cloud\bigquery string in it.
Also to be noted here is that the standard env only supports apps designed for GAE, executed through the sandbox, not generic, standalone apps. It's unclear if the basic app you tried is of one type or the other. See import cloudstorage, ImportError: No module named google.appengine.api.