Issue a GET request to IASystem with the given url
    and return a response in Collection+json format.
    :returns: http response with content in json

def __get_resource(dao, url):
    """
    Issue a GET request to IASystem with the given url
    and return a response in Collection+json format.
    :returns: http response with content in json
    """
    headers = {"Accept": "application/vnd.collection+json"}
    response = dao.getURL(url, headers)
    status = response.status
    logger.debug("{} ==status==> {}".format(url, status))

    if status != 200:
        message = str(response.data)

        if status == 404:
            # the URL not exists on the specific domain
            return None

        if status == 400:
            if "Term is out of range" in message:
                raise TermEvalNotCreated(url, status, message)

        raise DataFailureException(url, status, message)

    return json.loads(response.data)