NON_FIELD_ERRORS = '__all__'

    def __init__(self, message, code=None, params=None):

        import operator

        from django.utils.encoding import force_unicode

        """

        ValidationError can be passed any object that can be printed (usually

        a string), a list of objects or a dictionary.

        """

        if isinstance(message, dict):

            self.message_dict = message

            # Reduce each list of messages into a single list.

            message = reduce(operator.add, message.values())

        if isinstance(message, list):

            self.messages = [force_unicode(msg) for msg in message]

        else:

            self.code = code

            self.params = params

            message = force_unicode(message)

            self.messages = [message]

    def __str__(self):

        # This is needed because, without a __str__(), printing an exception

        # instance would result in this:

        # AttributeError: ValidationError instance has no attribute 'args'

        # See http://www.python.org/doc/current/tut/node10.html#handling

        if hasattr(self, 'message_dict'):

            return repr(self.message_dict)

        return repr(self.messages)

    def __repr__(self):

        if hasattr(self, 'message_dict'):

            return 'ValidationError(%s)' % repr(self.message_dict)

        return 'ValidationError(%s)' % repr(self.messages)

    def update_error_dict(self, error_dict):

        if hasattr(self, 'message_dict'):

            if error_dict:

                for k, v in self.message_dict.items():

                    error_dict.setdefault(k, []).extend(v)

            else:

                error_dict = self.message_dict

        else:

            error_dict[NON_FIELD_ERRORS] = self.messages

        return error_dict