Impossible to use custom user model in Django 1.7 due to AppRegistryNotReady exception

[ramusus]

Impossible to use custom user model in Django 1.7 due to AppRegistryNotReady exception:

django.core.exceptions.AppRegistryNotReady: Models aren't loaded yet.

[1337]

Django 1.7 has html email support though. Do you need to support this package beyond 1.6?

[ramusus]

Yes, I need below 1.6.
In Django 1.7 can I use html templates for all emails? Even in case of using third party apps, that provide only txt templates? Can I substitute these built-in txt templates with my own html versions? That was the main purpose of this app.