python 2.7 - django admin load error: ImportError at /admin/login/ No module named backends -

all of sudden, don't seem able access admin on django app. here's error message i'm getting, idea have happened? don't think changed admin or settings data since last opened it.

importerror @ /admin/login/ no module named backends request method: post request url: http://localhost:8000/admin/login/?next=/admin/ django version: 1.9.dev20150119161257 exception type: importerror exception value:
no module named backends exception location: /system/library/frameworks/python.framework/versions/2.7/lib/python2.7/importlib/init.py in import_module, line 37 python executable: /usr/bin/python python version: 2.7.6 python path:
['/users/saraabi/sites/django_testapp', '/library/python/2.7/site-packages/pip-6.0.6-py2.7.egg', '/users/saraabi/django-trunk', '/system/library/frameworks/python.framework/versions/2.7/lib/python27.zip', '/system/library/frameworks/python.framework/versions/2.7/lib/python2.7', '/system/library/frameworks/python.framework/versions/2.7/lib/python2.7/plat-darwin', '/system/library/frameworks/python.framework/versions/2.7/lib/python2.7/plat-mac', '/system/library/frameworks/python.framework/versions/2.7/lib/python2.7/plat-mac/lib-scriptpackages', '/system/library/frameworks/python.framework/versions/2.7/extras/lib/python', '/system/library/frameworks/python.framework/versions/2.7/lib/python2.7/lib-tk', '/system/library/frameworks/python.framework/versions/2.7/lib/python2.7/lib-old', '/system/library/frameworks/python.framework/versions/2.7/lib/python2.7/lib-dynload', '/system/library/frameworks/python.framework/versions/2.7/extras/lib/python/pyobjc', '/library/python/2.7/site-packages'] server time: thu, 16 jul 2015 23:31:24 +0000

environment:

request method: post request url: http://localhost:8000/admin/login/?next=/admin/

django version: 1.9.dev20150119161257 python version: 2.7.6 installed applications: ('django.contrib.admin', 'django.contrib.auth', 'django.contrib.contenttypes', 'django.contrib.sessions', 'django.contrib.messages', 'django.contrib.staticfiles', 'testapp') installed middleware: ('django.contrib.sessions.middleware.sessionmiddleware', 'django.middleware.common.commonmiddleware', 'django.middleware.csrf.csrfviewmiddleware', 'django.contrib.auth.middleware.authenticationmiddleware', 'django.contrib.auth.middleware.sessionauthenticationmiddleware', 'django.contrib.messages.middleware.messagemiddleware', 'django.middleware.clickjacking.xframeoptionsmiddleware', 'django.middleware.security.securitymiddleware')

traceback: file "/users/saraabi/django-trunk/django/core/handlers/base.py" in get_response 131. response = wrapped_callback(request, *callback_args, **callback_kwargs) file "/users/saraabi/django-trunk/django/views/decorators/cache.py" in _wrapped_view_func 54. response = view_func(request, *args, **kwargs) file "/users/saraabi/django-trunk/django/contrib/admin/sites.py" in login 388. return login(request, **defaults) file "/users/saraabi/django-trunk/django/views/decorators/debug.py" in sensitive_post_parameters_wrapper 76. return view(request, *args, **kwargs) file "/users/saraabi/django-trunk/django/utils/decorators.py" in _wrapped_view 110. response = view_func(request, *args, **kwargs) file "/users/saraabi/django-trunk/django/views/decorators/cache.py" in _wrapped_view_func 54. response = view_func(request, *args, **kwargs) file "/users/saraabi/django-trunk/django/contrib/auth/views.py" in login 40. if form.is_valid(): file "/users/saraabi/django-trunk/django/forms/forms.py" in is_valid 136. return self.is_bound , not self.errors file "/users/saraabi/django-trunk/django/forms/forms.py" in errors 128. self.full_clean() file "/users/saraabi/django-trunk/django/forms/forms.py" in full_clean 345. self._clean_form() file "/users/saraabi/django-trunk/django/forms/forms.py" in _clean_form 369. cleaned_data = self.clean() file "/users/saraabi/django-trunk/django/contrib/auth/forms.py" in clean 165. password=password) file "/users/saraabi/django-trunk/django/contrib/auth/init.py" in authenticate 60. backend, backend_path in _get_backends(return_tuples=true): file "/users/saraabi/django-trunk/django/contrib/auth/init.py" in _get_backends 27. backend = load_backend(backend_path) file "/users/saraabi/django-trunk/django/contrib/auth/init.py" in load_backend 21. return import_string(path)() file "/users/saraabi/django-trunk/django/utils/module_loading.py" in import_string 22. module = import_module(module_path) file "/system/library/frameworks/python.framework/versions/2.7/lib/python2.7/importlib/init.py" in import_module 37. import(name)

exception type: importerror @ /admin/login/ exception value: no module named backends

settings.py

import os base_dir = os.path.dirname(os.path.dirname(__file__)) project_dir = os.path.dirname(os.path.dirname(__file__) + '/../')  installed_apps = (     'django.contrib.admin',     'django.contrib.auth',     'django.contrib.contenttypes',     'django.contrib.sessions',     'django.contrib.messages',     'django.contrib.staticfiles',     'django.contrib.sites', )  template_context_processors = (     'django.contrib.auth.context_processors.auth',     'django.core.context_processors.request', )  middleware_classes = (     'django.contrib.sessions.middleware.sessionmiddleware',     'django.middleware.common.commonmiddleware',     'django.middleware.csrf.csrfviewmiddleware',     'django.contrib.auth.middleware.authenticationmiddleware',     'django.contrib.auth.middleware.sessionauthenticationmiddleware',     'django.contrib.messages.middleware.messagemiddleware',     'django.middleware.clickjacking.xframeoptionsmiddleware', ) site_id = 1  root_urlconf = 'apps.urls'  wsgi_application = 'apps.wsgi.application'  template_dirs = (     project_dir + '/templates/', )  databases = {     'default': {         'engine': 'django.db.backends.sqlite3',         'name': os.path.join(base_dir, 'db.sqlite3'),     } }