Mensagens de erro de login (wp-admin)

custom-error-msgs

<?php
/*
*
* Plugin Name: Mensagens de erro de login
* Description: Mensagens aleatórios e personalizadas para tentativas fracassadas de login.
* Version:     1.1
* Author:      LFreitas based on Sergio Costa (zergiocosta)
* Text Domain: custom-error-msgs
* 
* source: https://gist.github.com/zergiocosta/72f87176b236ed0c6e13
*
*/

// If this file is called directly, abort.
if ( ! defined( 'WPINC' ) ) {
	die;
}

function guwp_error_msgs() { 
	// insert how many msgs you want as an array item. it will be shown randomly 
	$custom_error_msgs = array(
		'<strong>YOU</strong> SHALL NOT PASS!',
		'<strong>HEY!</strong> GET OUT OF HERE!',
		'<strong>NO</strong>.',
		'Did you bring a <strong>shrubbery</strong>?',
	);
	// get random array item to show
	return $custom_error_msgs[array_rand($custom_error_msgs)];;
}
add_filter( 'login_errors', 'guwp_error_msgs' );
?>

Instead of changing in the functions.php, include as a site-specific plugin.
The file must be in /wp-content/plugins/ and the plugin must be active via WP Dashboard.

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Em vez de editar o functions.php, colocar como um plugin personalizado.
O arquivo deve estar na pasta /wp-content/plugins/ e o plugin deve ser ativado pelo Painel do WP.