my project is not running

Dear Sir,

I am having a project erppro

in pycharm environment it was running fine yesterday

But today it goes to doctest mode and give the following error.

please help
I am new in pycharm operation.

thank you
regards
sanat


/usr/bin/python2.6 /opt/erppro/exams/views/exam_center.py
Traceback (most recent call last):
  File "/opt/erppro/exams/views/exam_center.py", line 6, in <module>
    from django.core.cache import cache
  File "/usr/local/lib/python2.6/dist-packages/django/core/cache/__init__.py", line 77, in <module>
    if not settings.CACHES:
  File "/usr/local/lib/python2.6/dist-packages/django/utils/functional.py", line 276, in __getattr__
    self._setup()
  File "/usr/local/lib/python2.6/dist-packages/django/conf/__init__.py", line 40, in _setup
    raise ImportError("Settings cannot be imported, because environment variable %s is undefined." % ENVIRONMENT_VARIABLE)
ImportError: Settings cannot be imported, because environment variable DJANGO_SETTINGS_MODULE is undefined.

Process finished with exit code 1