Not seeing any error messages on failed login

[jrtilson]

When attempting to login with a regular username/email and password, I'm not presented with any errors on the form if the user enters invalid credentials. I do however see the following in the browser console:

Warning: setState(...): Can only update a mounted or mounting component. This usually means you called setState() on an unmounted component. This is a no-op. Please check the code for the LoginForm component.

I understand this a pretty common react issue, but I'm not sure why it's happening here. I managed to track it down to a this.showMessage call (which in turn calls this.setState) in a Meteor method callback, this one to be specific LoginForm.jsx

Any idea how to sort this out?