def _get_instance(resp):
    """
    Get the one and only match for the instance list in the response. If
    there are more or less and one match, log errors and return None.
    """
    instances = [i for r in resp['Reservations'] for i in r['Instances']]

    # return the one and only match
    if len(instances) == 1:
        return instances[0]