pewc_filter_validation_notice.php

<?php
/**
 * @param $message  The validation message
 * @param $label  	The field label
 * @param $item			The field object
 */
function prefix_filter_validation_notice( $message, $label, $item ) {
	$message = __( 'My new validation message for' );
	$message .= $label;
	return $message;
}
add_filter( 'pewc_filter_validation_notice', 'prefix_filter_validation_notice', 10, 3 );