Ember simple-auth mixins deprected

I am an experienced (55+ years) programmer but a total noob in ember and js. I'm trying to get a simple authentication page working using the ember-cli addons ember-cli-simple-auth, ember-cli-simple-auth-oauth2 and cut-and-paste from the simplelabs tutorial.

I get the following in the console:

DEPRECATION: The LoginControllerMixin is deprecated. Use the session's authenticate method directly instead.

and:

DEPRECATION: The AuthenticationControllerMixin is deprecated. Use the session's authenticate method directly instead.

The solution may be trivial, but I have been chasing it for hours and get deep into javascript before reaching a dead-end. The code that is causing these errors is:

import LoginControllerMixin from 'simple-auth/mixins/login-controller-mixin';

export default Ember.Controller.extend(LoginControllerMixin, { authenticator: 'simple-auth-authenticator:oauth2-password-grant' });

which invokes the ApplicationControllerMixin somewhere in the bower code.

Before I "re-invent the wheel" by translating some old html/ruby/pascal code into js, can anyone help me "Use the session's authenticate method directly instead."?

Thanks.