Hi there,
Awesome app, by the way.
I received the error in the title after trying to authenticate a test email (perhaps I performed setup incorrectly somehow), but it was easily fixed by following the steps from this link: http://spottedsun.com/django-registration-activation-error-for-django-1-4/. I just applied the same principle to code around line 155 of the emailactivation/models.py file.
Perhaps this was an annoying bug in my system, but it is fixed for now, unless I drastically messed up my own code.
Best of luck!