title: Forbidden Error on get_thing_shadow with boto3, aws iot and alexa
body: <p>I am running a custom alexa skill with flask-ask that connects to aws iot.
  Using same credentials work when running the script on local machine and using ngrok to assign to Alexa skill endpoint. But when I use zappa to upload as lambda, I get the following:</p>
  
  <pre><code>File "/var/task/main.py", line 48, in get_shadow
  res=client.get_thing_shadow(thingName="test_light")
  File "/var/runtime/botocore/client.py", line 253, in _api_call
  return self._make_api_call(operation_name, kwargs)
  File "/var/runtime/botocore/client.py", line 543, in _make_api_call
  raise error_class(parsed_response, operation_name)
  ClientError: An error occurred (ForbiddenException) when calling the GetThingShadow operation: Forbidden
  </code></pre>
  
  <p>When using ngrok, the skill works completely fine. What am I missing here? Help!</p>