An aptdeamon regression update has been released for Debian 6 LTS

Package : aptdaemon
Version : 0.31+bzr413-1.1+deb6u2
Debian Bug : 791469

It was reported that version 0.31+bzr413-1.1+deb6u1 of aptdaemon (which
fixed CVE-2015-1323) was not installable if you have Python 2.5 installed.

This has been fixed in version 0.31+bzr413-1.1+deb6u2.

  Aptdaemon regression update for Debian 6 LTS