def null_validator(*args, **kwargs):
    """A validator that doesn't validate anything.

    This is somewhat lame, but if you have a "Cancel" type button that
    won't want to validate the form, you need something like this.

    @form.action(_(u"label_cancel", default=u"Cancel"),
                 validator=null_validator,
                 name=u'cancel')
    """
    return ()