'Add only the required message, but no \'ng-required\' attribute to the input fields,
otherwise all Checkboxes of a MultipleChoiceField would require the property "checked".'

def get_multiple_choices_required(self):

    errors = []
    if self.required:
        for (key, msg) in self.error_messages.items():
            if (key == u'required'):
                errors.append((u'$error.required', msg))
    return errors
