'Low level xmlid lookup
Return (id, res_model, res_id) or raise ValueError if not found'

@api.model
@tools.ormcache('xmlid')
def xmlid_lookup(self, xmlid):

    (module, name) = xmlid.split('.', 1)
    xid = self.search([('module', '=', module), ('name', '=', name)])
    if (not xid):
        raise ValueError(('External    ID    not    found    in    the    system:    %s' % xmlid))
    res = xid.read(['model', 'res_id'])[0]
    if (not res['res_id']):
        raise ValueError(('External    ID    not    found    in    the    system:    %s' % xmlid))
    return (res['id'], res['model'], res['res_id'])
