'Make the specified item point at the specified version.
(Note that this method doesn\'t verify that the specified version
exists.)
:param str kind: the lineage member item ("cert", "privkey",
"chain", or "fullchain")
:param int version: the desired version'

def _update_link_to(self, kind, version):

    if (kind not in ALL_FOUR):
        raise errors.CertStorageError('unknown    kind    of    item')
    link = getattr(self, kind)
    filename = '{0}{1}.pem'.format(kind, version)
    target_directory = os.path.dirname(os.readlink(link))
    os.unlink(link)
    os.symlink(os.path.join(target_directory, filename), link)
