How to change registration Email content?

<?php
/*
Plugin Name: Custom New User Email
Description: Changes the copy in the email sent out to new users
*/

// Redefine user notification function
if ( !function_exists('wp_new_user_notification') ) {
	function wp_new_user_notification( $user_id, $plaintext_pass = '' ) {
		$user = new WP_User($user_id);

		$user_login = stripslashes($user->user_login);
		$user_email = stripslashes($user->user_email);

		$message  = sprintf(__('Nouvelle inscription %s:'), get_option('blogname')) . "rnrn";
		$message .= sprintf(__('Identifiant: %s'), $user_login) . "rnrn";
		$message .= sprintf(__('E-mail: %s'), $user_email) . "rn";

		@wp_mail(get_option('admin_email'), sprintf(__('[%s] New User Registration'), get_option('blogname')), $message);

		if ( empty($plaintext_pass) )
			return;

		$message  = __('Bonjour,') . "rnrn";
		$message .= sprintf(__("Merci de vous être inscrit au site de la %s! Voici votre identifiant et mot de passe:")) . "rnrn";
		$message .= sprintf(__('Identifiant: %s'), $user_login) . "rn";
		$message .= sprintf(__('Mot de passe: %s'), $plaintext_pass) . "rnrn";
		$message .= sprintf(__('Si vous avez un problème, merci de nous contacter: %s.'), get_option('admin_email')) . "rnrn";
		$message .= __('Merci');

		wp_mail($user_email, sprintf(__('[%s] Your username and password'), get_option('blogname')), $message);

	}
}

?>