def get_errid(errobj):
    """
    fetch the YYYY:NNNN part from an errata dict object
    basically strips off the CLA/RHSA etc prefix

    parameters:
        errobj(dict): dict representing an erratum in RHN

    returns:
        string: YYYY:NNNN from an erratum
    """
    return errobj.get('advisory').split('-')[1]
