Unittests RESTful API – django.core.exceptions.ImproperlyConfigured: Requested setting INSTALLED_APPS, but settings are not configured

Когда пытаюсь запустить тесты, интерпретатор выдает следующую ошибку:

>     django.core.exceptions.ImproperlyConfigured: Requested setting INSTALLED_APPS, but settings are not configured. You must either > define the environment variable DJANGO_SETTINGS_MODULE or call > settings.configure() before accessing settings. 

Всем ответам заранее благодарен.