Redefining class attributes in derived model classes, Django
class CustomUser(User):
  """The inherited User class. Email field are redefined to add the warning
  about uniqueness is required. UserManager as the default manager so that
  the standard methods are available."""

  def __init__(self, *args, **kwargs):
      super(CustomUser, self).__init__(*args, **kwargs)
      email = models.EmailField(unique=True)
      email.contribute_to_class(u'email', self)

  objects = UserManager()

File "/home/i159/Envs/students/lib/python2.6/site-packages/django/core/handlers/base.py"     in get_response
  111.                         response = callback(request, *callback_args,   **callback_kwargs)
File "/home/i159/Envs/students/lib/python2.6/site-packages/django/contrib/admin/options.py" in wrapper
  307.                 return self.admin_site.admin_view(view)(*args, **kwargs)
File "/home/i159/Envs/students/lib/python2.6/site-packages/django/utils/decorators.py" in _wrapped_view
  93.                     response = view_func(request, *args, **kwargs)
File "/home/i159/Envs/students/lib/python2.6/site-packages/django/views/decorators/cache.py" in _wrapped_view_func
  79.         response = view_func(request, *args, **kwargs)
File "/home/i159/Envs/students/lib/python2.6/site-packages/django/contrib/admin/sites.py" in inner
  196.                 return self.login(request)
File "/home/i159/Envs/students/lib/python2.6/site-packages/django/views/decorators/cache.py" in _wrapped_view_func
  79.         response = view_func(request, *args, **kwargs)
File "/home/i159/Envs/students/lib/python2.6/site-packages/django/contrib/admin/sites.py" in login
  331.         return login(request, **defaults)
File "/home/i159/Envs/students/lib/python2.6/site-packages/django/utils/decorators.py" in _wrapped_view
  93.                     response = view_func(request, *args, **kwargs)
File "/home/i159/Envs/students/lib/python2.6/site-packages/django/views/decorators/cache.py" in _wrapped_view_func
  79.         response = view_func(request, *args, **kwargs)
File "/home/i159/Envs/students/lib/python2.6/site-packages/django/contrib/auth/views.py" in login
  35.         if form.is_valid():
File "/home/i159/Envs/students/lib/python2.6/site-packages/django/forms/forms.py" in is_valid
  121.         return self.is_bound and not bool(self.errors)
File "/home/i159/Envs/students/lib/python2.6/site-packages/django/forms/forms.py" in _get_errors
  112.             self.full_clean()
File "/home/i159/Envs/students/lib/python2.6/site-packages/django/forms/forms.py" in full_clean
  268.         self._clean_form()
File "/home/i159/Envs/students/lib/python2.6/site-packages/django/forms/forms.py" in _clean_form
  296.             self.cleaned_data = self.clean()
File "/home/i159/Envs/students/lib/python2.6/site-packages/django/contrib/admin/forms.py" in clean
  26.             self.user_cache = authenticate(username=username, password=password)
File "/home/i159/Envs/students/lib/python2.6/site-packages/django/contrib/auth/__init__.py" in authenticate
  55.             user = backend.authenticate(**credentials)
File "/home/i159/workspace/students/backends.py" in authenticate
  15.         print self.user_class()
File "/home/i159/workspace/students/stdapp/models.py" in __init__
  13.         email.contribute_to_class(u'email', self)
File "/home/i159/Envs/students/lib/python2.6/site-packages/django/db/models/fields/__init__.py" in contribute_to_class
  235.         self.set_attributes_from_name(name)
File "/home/i159/Envs/students/lib/python2.6/site-packages/django/db/models/fields/__init__.py" in set_attributes_from_name
  232.             self.verbose_name = name.replace('_', ' ')

Exception Type: AttributeError at /admin/stdapp/customuser/add/
Exception Value: 'CustomUser' object has no attribute 'replace'

class CustomUser(User):
    def __init__(self, *args, **kwargs):
        setattr(self._meta.fields[4], 'unique', True)

class CustomUser(User):
    def __init__(self, *args, **kwargs):
        self._meta.fields[4].unique=True