1. Copy paste code from https://cloud.google.com/spanner/docs/getting-started/python/
2. Run

... it hangs forever

3. Waste Spend hour struggling to figure out what is happening.

4. Figure out how to turn on http logging with,

   import logging
   
   logging.basicConfig(level=logging.DEBUG)
   

5. See:

   DEBUG:google.auth.transport.requests:Making request: POST https://oauth2.googleapis.com/token
   DEBUG:urllib3.connectionpool:https://oauth2.googleapis.com:443 "POST /token HTTP/1.1" 400 None
   ERROR:grpc._plugin_wrapping:AuthMetadataPluginCallback "<google.auth.transport.grpc.AuthMetadataPlugin object at 0x10d79d4a8>" raised exception!
   Traceback (most recent call last):
   File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/grpc/_plugin_wrapping.py", line 79, in __call__
       callback_state, callback))
   File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/google/auth/transport/grpc.py", line 77, in __call__
       callback(self._get_authorization_headers(context), None)
   File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/google/auth/transport/grpc.py", line 65, in _get_authorization_headers
       headers)
   File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/google/auth/credentials.py", line 122, in before_request
       self.refresh(request)
   File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/google/oauth2/service_account.py", line 322, in refresh
       request, self._token_uri, assertion)
   File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/google/oauth2/_client.py", line 145, in jwt_grant
       response_data = _token_endpoint_request(request, token_uri, body)
   File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/google/oauth2/_client.py", line 111, in _token_endpoint_request
       _handle_error_response(response_body)
   File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/google/oauth2/_client.py", line 61, in _handle_error_response
       error_details, response_body)
   google.auth.exceptions.RefreshError: ('invalid_grant: Not a valid email or user ID.', '{\n  "error": "invalid_grant",\n  "error_description": "Not a valid email or user ID."\n}')
   DEBUG:google.api_core.retry:Retrying due to 503 Getting metadata from plugin failed with error: ('invalid_grant: Not a valid email or user ID.', '{\n  "error": "invalid_grant",\n  "error_description": "Not a valid email or user ID."\n}'), sleeping 1.3s ...
   

This is an error that will never resolve. We should surface it to the user immediately.

Also: I have no idea why this is a 503 UNAVAILABLE. Why would it not be a 400 BAD REQUEST or 401 UNAUTHORIZED??