Why am I getting ImportError: from askbot.models import signals

edit

I've been trying to get Askbot to work in production and I keep getting this stack trace when I attempt to Migrate or enter the Shell.
Everything works fine on my development computer.
What's going wrong?

  File "manage.py", line 11, in <module>  
    execute_manager(settings)  
  File "/home/spirituality/webapps/askbot/lib/python2.7/django/core/management/__init__.py", line 438, in execute_manager  
    utility.execute()  
  File "/home/spirituality/webapps/askbot/lib/python2.7/django/core/management/__init__.py", line 379, in execute  
    self.fetch_command(subcommand).run_from_argv(self.argv)  
  File "/home/spirituality/webapps/askbot/lib/python2.7/django/core/management/base.py", line 191, in run_from_argv  
    self.execute(*args, **options.__dict__)  
  File "/home/spirituality/webapps/askbot/lib/python2.7/django/core/management/base.py", line 220, in execute  
    output = self.handle(*args, **options)  
  File "/home/spirituality/webapps/askbot/lib/python2.7/django/core/management/base.py", line 351, in handle  
    return self.handle_noargs(**options)  
  File "/home/spirituality/webapps/askbot/lib/python2.7/django/core/management/commands/shell.py", line 47, in handle_noargs  
    loaded_models = get_models()  
  File "/home/spirituality/webapps/askbot/lib/python2.7/django/db/models/loading.py", line 167, in get_models  
    self._populate()  
  File "/home/spirituality/webapps/askbot/lib/python2.7/django/db/models/loading.py", line 64, in _populate  
    self.load_app(app_name)  
  File "/home/spirituality/webapps/askbot/lib/python2.7/django/db/models/loading.py", line 78, in load_app  
    models = import_module('.models', app_name)  
  File "/home/spirituality/webapps/askbot/lib/python2.7/django/utils/importlib.py", line 35, in import_module  
    __import__(name)  
  File "/home/spirituality/webapps/askbot/askbot-discussion/askbot/models/__init__.py", line 71, in <module>  
    from askbot.models import signals  
ImportError: cannot import name signals