With latest localstack image running in Docker, when publishing a message to a non-existent SNS topic no error is thrown.  This differs from AWS.
if subscriber.get('RawMessageDelivery') not in ('true', True):
        return {}
    message_attributes = {}
    for key, value in attributes.items():
        attribute = {}
        attribute['DataType'] = value['Type']
        if value['Type'] == 'Binary':
            attribute['BinaryValue'] = value['Value']
        else:
            attribute['StringValue'] = value['Value']
        message_attributes[key] = attribute
    return message_attributes
def get_message_attributes(req_data):