warn on failed login

lib/passport.js

@@ -60,6 +60,7 @@ module.exports.login = (req, res, next) => {
             return next(err);
         }
         if (!user) {
+            log.warn('auth', `[client ${req.ip}] authentication failure`);
             req.flash('danger', info && info.message || _('Failed to authenticate user'));
             return res.redirect('/users/login' + (req.body.next ? '?next=' + encodeURIComponent(req.body.next) : ''));
         }