Check if cookies are enabled during login

/**
 * This code snippet is a custom login error.
 * It applies the same logic as the wp-login.php to determine if cookies 
 * are enabled prior to setting the user as logged in.  If cookies
 * are not enabled, it returns the login error message from core WP.
 */
add_filter( 'wpmem_after_wp_signon', function( $user ) {
    if ( empty( $_COOKIE[ TEST_COOKIE ] ) ) {
        // If cookies are disabled, the user can't log in even with a valid username and password.
        $user = new WP_Error(
            'test_cookie',
            sprintf(
                /* translators: %s: Browser cookie documentation URL. */
                __( '<strong>Error:</strong> Cookies are blocked or not supported by your browser. You must <a href="%s">enable cookies</a> to use WordPress.' ),
                __( 'https://developer.wordpress.org/advanced-administration/wordpress/cookies/#enable-cookies-in-your-browser' )
            )
        );
    }
    return $user;
});