What would cause a SystemExit exception?

edit

I just updated askbot-discussion.

The django.wsgi configuration is identical to what I had before the update.

$ cat django.wsgi

import os  
import sys  

current_directory = os.path.dirname(__file__)  
parent_directory = os.path.dirname(current_directory)  
module_name = os.path.basename(current_directory)  

sys.path.append(parent_directory)  
sys.path.append(current_directory)  
os.environ['DJANGO_SETTINGS_MODULE'] = '%s.settings' % module_name  
import django.core.handlers.wsgi  
application = django.core.handlers.wsgi.WSGIHandler()

Here is the traceback:

[Thu Dec 06 11:24:02 2012] [error] [client 127.0.0.1] mod_wsgi (pid=7183): SystemExit exception raised by WSGI script '/home/username/webapps/askbot/askbotSpirit/django.wsgi' ignored.  
[Thu Dec 06 11:24:02 2012] [error] [client 127.0.0.1] Traceback (most recent call last):  
[Thu Dec 06 11:24:02 2012] [error] [client 127.0.0.1]   File "/home/username/lib/python2.7/Django-1.3.1-py2.7.egg/django/core/handlers/wsgi.py", line 250, in __call__  
[Thu Dec 06 11:24:02 2012] [error] [client 127.0.0.1]     self.load_middleware()  
[Thu Dec 06 11:24:02 2012] [error] [client 127.0.0.1]   File "/home/username/lib/python2.7/Django-1.3.1-py2.7.egg/django/core/handlers/base.py", line 45, in load_middleware  
[Thu Dec 06 11:24:02 2012] [error] [client 127.0.0.1]     mod = import_module(mw_module)  
[Thu Dec 06 11:24:02 2012] [error] [client 127.0.0.1]   File "/home/username/lib/python2.7/Django-1.3.1-py2.7.egg/django/utils/importlib.py", line 35, in import_module  
[Thu Dec 06 11:24:02 2012] [error] [client 127.0.0.1]     __import__(name)  
[Thu Dec 06 11:24:02 2012] [error] [client 127.0.0.1]   File "/home/username/webapps/askbot/askbot-discussion/askbot/middleware/view_log.py", line 7, in <module>  
[Thu Dec 06 11:24:02 2012] [error] [client 127.0.0.1]     from askbot.models import signals  
[Thu Dec 06 11:24:02 2012] [error] [client 127.0.0.1]   File "/home/username/webapps/askbot/askbot-discussion/askbot/models/__init__.py", line 2, in <module>  
[Thu Dec 06 11:24:02 2012] [error] [client 127.0.0.1]     startup_procedures.run()  
[Thu Dec 06 11:24:02 2012] [error] [client 127.0.0.1]   File "/home/username/lib/python2.7/Django-1.3.1-py2.7.egg/django/db/transaction.py", line 217, in inner  
[Thu Dec 06 11:24:02 2012] [error] [client 127.0.0.1]     res = func(*args, **kwargs)  
[Thu Dec 06 11:24:02 2012] [error] [client 127.0.0.1]   File "/home/username/webapps/askbot/askbot-discussion/askbot/startup_procedures.py", line 886, in run  
[Thu Dec 06 11:24:02 2012] [error] [client 127.0.0.1]     sys.exit(1)  
[Thu Dec 06 11:24:02 2012] [error] [client 127.0.0.1] SystemExit: 1