/* Main redirection of the default login page */
function qs_redirect_login_page() {
	$login_page  = home_url('login');
	$page_viewed = basename($_SERVER['REQUEST_URI']);

	if($page_viewed == "wp-login.php" && $_SERVER['REQUEST_METHOD'] == 'GET') {
		wp_redirect($login_page);
		exit;
	}
}
add_action('init','qs_redirect_login_page');

/* Where to go if a login failed */
function qs_custom_login_failed() {
	$login_page  = home_url('login');
	wp_redirect($login_page . '?login=failed');
	exit;
}
add_action('wp_login_failed', 'qs_custom_login_failed');

/* Where to go if any of the fields were empty */
function qs_verify_user_pass($user, $username, $password) {
	$login_page  = home_url('login');
	if($username == "" || $password == "") {
		wp_redirect($login_page . "?login=empty");
		exit;
	}
}
add_filter('authenticate', 'qs_verify_user_pass', 1, 3);