Comment 1 for bug 273979

The problem is that the version of apt-cdrom (or rather the implementation in libapt) for "apt-cdrom add" checks all files in the Release file. If they are missing, it fails. The version of apt in intrepid has the required changes to make apt not fail if the Release file has files that are not on the CD.

So either update-manager needs to work around the issue or we need to add a backported apt+python-apt with the fix to the CD as prerequisites.