It looks like you have upgraded to Django 1.4 or later.
The auth context processor has been moved from django.core.context_processors.auth to django.contrib.auth.context_processors.auth. The move started in Django 1.2, and django.core.context_processors.auth was completely removed in Django 1.4.
I recommend you run the same version of Django on your dev and production environments to prevent errors like this.
When you upgrade to Django 1.4, you need to make the following change to TEMPLATE_CONTEXT_PROCESSORS in your settings file:
TEMPLATE_CONTEXT_PROCESSORS = ("django.core.context_processors.auth",
TEMPLATE_CONTEXT_PROCESSORS = ("django.contrib.auth.context_processors.auth",
The problem seems to be from developing PlugUI with an older (1.2?) version of django, and changes that were implemented with or before django 1.4, which is the version that's automatically installed by pacman when you follow the directions in the original post.
Edit settings.py in /opt/PlugUI and change the line (bolded) to match. You might need to restart the daemon.
Changing that one line fixed the error and gave me a "Create Default User" screen.