add a new Item class object

def addItem(self, item, message=None):
        """add a new Item class object"""
        if message is None:
            message = 'Adding item %s' % item.path
        try:
            v = Version.new(repo=self)
            v.addItem(item)
            v.save(message)
        except VersionError, e:
            raise RepoError(e)