I've installed a clean ezplatform_2015_12, without demo bundle, and I've been playing with a clean design. When I got to the login page, I ran into a variable does not exist error.

I used the example for login.html.twig present in Authentication doc page.

The example shows csrf_token being introduced as

<input type="hidden" name="_csrf_token" value="{{ csrf_token }}" />

but this variable does not seem to exist.

What works for me is to use what is in ezpublish core security template:

<input type="hidden" name="_csrf_token" value="{{ csrf_token("authenticate") }}" />