Stop non-approved users from logging in.

pmpro-approvals-login-example.php

<?php
/**
 * This is an example to stop non-approved user's from logging in using the Approvals Add On For Paid Memberships Pro.
 * Add this code below to your PMPro Customizations Plugin - https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
 
 function my_pmpro_stop_users_logging_in( $user, $password ) {
	
	$user_id = $user->ID;
	
	if( !empty( $user_id ) ) {
		$level = pmpro_getMembershipLevelForUser( $user_id );
		// Get approval status
		if( class_exists( 'PMPro_Approvals') ) {
			$approval = PMPro_Approvals::getUserApproval( $user_id );
			// User currently does not need approval.
			if ( empty( $approval ) ) {
				return $user;
			}
			$approval_status = $approval['status'];
			if ( ! empty( $approval_status ) && $approval_status != 'approved' ) {
				$access = false;
			} else {
				$access = true;
			}
		}
	}

	if ( ! $access ) {
		return;
	}

	return $user;
}
add_filter( 'wp_authenticate_user', 'my_pmpro_stop_users_logging_in', 10, 2 );

Hello there, thanks a lot, how it is possible to add a custom error message? thanks