required-user-mixin.py

from django.http import HttpResponseForbidden

class RequiredGroupMixin(object):
    """
    Ensure only logged in users who belong to a particular group (or groups)
    can access this view.

    To use this Mixin, just include it as a subclass to your view and add a
    new attribute, `restrict_to_groups`, as an iterable of allowed group names.

    For example, if you want to restrict this view to only users in the group
    'Students' you'd set `restrict_to_groups` like so:

    restrict_to_groups = ('Students',)
    """
    def dispatch(self, request, *args, **kwargs):
        if hasattr(self, 'restrict_to_groups'):
            allowed_groups = request.user.groups.filter(
                name__in=self.restrict_to_groups
            )
            if not allowed_groups:
                forbidden_message = 'You are not allowed to view this page.'
                if request.user.is_superuser is True:
                    forbidden_message = (
                        'Only users that belong to the following groups may '
                        'access this page: {}'.format(
                            ', '.join(self.restrict_to_groups)
                        )
                    )
                return HttpResponseForbidden(forbidden_message)
        return super(RequiredGroupMixin, self).dispatch(
            request, *args, **kwargs
        )