Changelogs not retrievable

[Rico Tzschichholz]

aptitude is not able to fetch changelogs while apt-get happily does it in the same environment.

~$ aptitude changelog sed
Err Changelog of sed
E: Changelog download failed: 404 Not Found
E: You must put some 'source' URIs in your sources.list
E: Couldn't find a changelog for sed

~$ apt-get changelog sed
Get:1 Changelog for sed (http://changelogs.ubuntu.com/changelogs/pool/main/s/sed/sed_4.2.2-4ubuntu1/changelog) [20.3 kB]
Fetched 20.3 kB in 0s (83.9 kB/s)

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: aptitude 0.6.11-1ubuntu2
ProcVersionSignature: Ubuntu 3.16.0-23.31-generic 3.16.4
Uname: Linux 3.16.0-23-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.14.7-0ubuntu8
Architecture: amd64
CurrentDesktop: GNOME
Date: Tue Oct 28 15:56:13 2014
InstallationDate: Installed on 2010-03-15 (1688 days ago)
InstallationMedia: Ubuntu 10.04 "Lucid Lynx" - Alpha amd64 (20100314)
SourcePackage: aptitude
UpgradeStatus: No upgrade log present (probably fresh install)