can't initialize interface: dialog - fall back on interface: readline

[Sam_]

Message appears during upgrade. (translated from german)
Terminal output:
debconf: can't initialize interface: Dialog
debconf: (No appropriate Dialog-Program installed, thus Dialog-Interface can't be used.
at /usr/share/perl5/Debconf/FrontEnd/Dialog.pm line 75, <> line 50.)
debconf: fall back on interface: Readline

Message repeated twice with
at /usr/share/perl5/Debconf/FrontEnd/Dialog.pm line 75.)

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: debconf 1.5.41ubuntu2
ProcVersionSignature: Ubuntu 3.2.0-15.24-generic 3.2.5
Uname: Linux 3.2.0-15-generic x86_64
ApportVersion: 1.91-0ubuntu1
Architecture: amd64
Date: Sat Feb 11 17:03:23 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Alpha amd64 (20120204)
PackageArchitecture: all
ProcEnviron:
 PATH=(custom, no user)
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: debconf
UpgradeStatus: No upgrade log present (probably fresh install)

[Andreas Moog (ampelbein)]

Should be fixed in debconf-1.5.41ubuntu2