ImportError в admin.autodiscover() при попытке запустить одиночный тест django-nose

Я пытаюсь запустить одиночный тест, используя django-nose:

./manage.py test lead.tests:LeadStatTests.basic_stat_test

И происходит следующее ImportError:

======================================================================
ERROR: Failure: ImportError (cannot import name LeadSource)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/nose/loader.py", line 420, in loadTestsFromName
    addr.filename, addr.module)
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/nose/importer.py", line 47, in importFromPath
    return self.importFromDir(dir_path, fqname)
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/nose/importer.py", line 94, in importFromDir
    mod = load_module(part_fqname, fh, filename, desc)
  File "/Users/kolen/items/someproject/lead/tests.py", line 16, in <module>
    from lead.models import Lead, Action, LeadSource, LeadType, events_by_month, EventSummary
  File "/Users/kolen/items/someproject/lead/models.py", line 38, in <module>
    User = get_user_model()
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/django/contrib/auth/__init__.py", line 127, in get_user_model
    user_model = get_model(app_label, model_name)
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/django/db/models/loading.py", line 271, in get_model
    self._populate()
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/django/db/models/loading.py", line 78, in _populate
    self.load_app(app_name)
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/django/db/models/loading.py", line 99, in load_app
    models = import_module('%s.models' % app_name)
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/django/utils/importlib.py", line 40, in import_module
    __import__(name)
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/debug_toolbar/models.py", line 63, in <module>
    patch_root_urlconf()
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/debug_toolbar/models.py", line 51, in patch_root_urlconf
    reverse('djdt:render_panel')
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/django/core/urlresolvers.py", line 507, in reverse
    app_list = resolver.app_dict[ns]
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/django/core/urlresolvers.py", line 329, in app_dict
    self._populate()
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/django/core/urlresolvers.py", line 267, in _populate
    for pattern in reversed(self.url_patterns):
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/django/core/urlresolvers.py", line 365, in url_patterns
    patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/django/core/urlresolvers.py", line 360, in urlconf_module
    self._urlconf_module = import_module(self.urlconf_name)
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/django/utils/importlib.py", line 40, in import_module
    __import__(name)
  File "/Users/kolen/items/someproject/system/urls.py", line 8, in <module>
    admin.autodiscover()
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/django/contrib/admin/__init__.py", line 29, in autodiscover
    import_module('%s.admin' % app)
  File "/Users/kolen/.virtualenvs/someenv/lib/python2.7/site-packages/django/utils/importlib.py", line 40, in import_module
    __import__(name)
  File "/Users/kolen/items/someproject/lead/admin.py", line 5, in <module>
    from lead.models import LeadSource, LeadType, Lead, ........, \
ImportError: cannot import name LeadSource

Запуск всех тестов с ./manage.py test работает. Это исключение возникает только при попытке запустить отдельный тест или тестовый класс. Однако запуск всех тестов занимает слишком много времени, поэтому я хочу запустить один тест.

Приложение и администратор django тоже работают. В корневом каталоге проекта нет __init__.py.