Validates the uniqueness of fields, but also handles the localized_fields.

def validate_unique(self):
        """
        Validates the uniqueness of fields, but also handles the localized_fields.
        """
        form_errors = []
        try:
            super(LocalisedForm, self).validate_unique()
        except ValidationError as e:
            form_errors += e.messages

        # add unique validation for the localized fields.
        localized_fields_checks = self._get_localized_field_checks()
        bad_fields = set()

        field_errors, global_errors = self._perform_unique_localized_field_checks(localized_fields_checks)
        bad_fields.union(field_errors)
        form_errors.extend(global_errors)
        
        for field_name in bad_fields:
            del self.cleaned_data[field_name]
        if form_errors:
            # Raise the unique together errors since they are considered
            # form-wide.
            raise ValidationError(form_errors)