Pycharm 3.0.2：无法附加测试报告给测试框架或测试框架意外退出

Question

在Pycharm中运行测试时，我突然遇到此错误。

 Testing started at 15:11 ...
 Traceback (most recent call last):


File "C:\Program Files (x86)\JetBrains\PyCharm 3.0.2\helpers\pycharm\django_test_manage.py", line 18, in <module>
    import django_test_runner
  File "C:\Program Files (x86)\JetBrains\PyCharm 3.0.2\helpers\pycharm\django_test_runner.py", line 3, in <module>
    from tcunittest import TeamcityTestRunner
  File "C:\Program Files (x86)\JetBrains\PyCharm 3.0.2\helpers\pycharm\tcunittest.py", line 2, in <module>
    from unittest import TestResult
ImportError: cannot import name TestResult

Process finished with exit code 1

有谁知道可能导致这种情况的原因？

PS - from unittest import TestResult在（virtualenv）shell

中正常工作