Wrapper for log4r warn
qgert_log_warn(plogger, ps_caller, ps_msg)
log4r logger object
function from which we are called
logging message
if (FALSE) {
qgert_logger <- get_qgert_logger()
qgert_log_level(qgert_logger, 'WARN')
qgert_log_warn(qgert_logger, 'Examples', 'test message')
}