Normally S3 objects in localstack can be accessed via `http://localhost:4572/bucket/key`.

However, if the object is 7 MBs or larger, attempting to access it via this URL will result in a 403 error. Objects any smaller are retrieved as expected.

(Possibly related: Lambda response size is limited to 6MB. Perhaps that is being used by accident?)
'ddblocal:([^"]+)"', r'\1: "arn:aws:dynamodb:%s:\2"' % aws_stack.get_region(),
            to_str(response._content))
            if content_replaced != response._content:
                response._content = content_replaced
                fix_headers_for_updated_response(response)
        action = headers.get('X-Amz-Target')
        if not action:
            return
        record = {
            'eventID': '1',
            'eventVersion': '1.0',
            'dynamodb': {
                'StreamViewType': 'NEW_AND_OLD_IMAGES',
                'SizeBytes': -1
            },
            'awsRegion': aws_stack.get_region(),
            'eventSource': 'aws:dynamodb'
        }
        records = [record]
        if action == '%s.UpdateItem' % ACTION_PREFIX:
            if response.status_code == 200:
                updated_item = find_existing_item(data)
                if not updated_item:
                    return
                record['eventName'] = 'MODIFY'
                record['dynamodb']['Keys'] = data['Key']
                record['dynamodb']['OldImage'] = self._thread_local('existing_item')
                record['dynamodb']['NewImage'] = updated_item
                record['dynamodb']['SizeBytes'] = len(json.dumps(updated_item))
        elif action == '%s.BatchWriteItem' % ACTION_PREFIX: