PyCharm Django的测试运行器无法看到django.sites（运行时错误）

当我运行manage.py test一切工作正常，但如果与PyCharm Django的运行试验测试中，它给了我以下错误：PyCharm Django的测试运行器无法看到django.sites（运行时错误）

Error 
Traceback (most recent call last): 
    File "/usr/lib/python3.4/unittest/case.py", line 58, in testPartExecutor 
    yield 
    File "/usr/lib/python3.4/unittest/case.py", line 577, in run 
    testMethod() 
    File "/usr/lib/python3.4/unittest/loader.py", line 32, in testFailure 
    raise exception 
ImportError: Failed to import test module: order_form.tests 
Traceback (most recent call last): 
    File "/usr/lib/python3.4/unittest/loader.py", line 312, in _find_tests 
    module = self._get_module_from_name(name) 
    File "/usr/lib/python3.4/unittest/loader.py", line 290, in _get_module_from_name 
    __import__(name) 
    File "/home/vagrant/project/order_form/tests.py", line 2, in <module> 
    from .models import Order 
    File "/home/vagrant/project/order_form/models.py", line 3, in <module> 
    from cms.models.pluginmodel import CMSPlugin 
    File "/home/vagrant/.virtualenvs/env/lib/python3.4/site-packages/cms/models/__init__.py", line 3, in <module> 
    from .pagemodel import * # nopyflakes 
    File "/home/vagrant/.virtualenvs/env/lib/python3.4/site-packages/cms/models/pagemodel.py", line 6, in <module> 
    from django.contrib.sites.models import Site 
    File "/home/vagrant/.virtualenvs/env/lib/python3.4/site-packages/django/contrib/sites/models.py", line 83, in <module> 
    class Site(models.Model): 
    File "/home/vagrant/.virtualenvs/env/lib/python3.4/site-packages/django/db/models/base.py", line 102, in __new__ 
    "INSTALLED_APPS." % (module, name) 
RuntimeError: Model class django.contrib.sites.models.Site doesn't declare an explicit app_label and isn't in an application in INSTALLED_APPS.

是，我已启用'django.contrib.sites'in INSTALLED_APPS并设置了SITE_ID。