software center takes ages to open installation file

[sevku]

When I open an installation file (.deb) the software center opens as supposed. But it only shows the start page for quite a while. I was using Fedora before where it instantly shows the installation page, so it seemed broken in Ubuntu. However, when reporting the bug it was the first time I was waiting long enough until it opened the installation page.
This took me weeks to figure out that it isn't broken but takes minutes until it opens. I hope this process can be sped up.

There was a similar bug reported before: #666956
However, it was marked as Fix Released years ago.

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: software-center 13.10-0ubuntu12
ProcVersionSignature: Ubuntu 4.2.0-16.19-generic 4.2.3
Uname: Linux 4.2.0-16-generic x86_64
ApportVersion: 2.19.1-0ubuntu4
Architecture: amd64
CurrentDesktop: Unity
Date: Wed Nov 4 12:09:48 2015
ExecutablePath: /usr/share/software-center/software-center
InstallationDate: Installed on 2015-08-13 (82 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
InterpreterPath: /usr/bin/python2.7
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=de_DE
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: software-center
UpgradeStatus: Upgraded to wily on 2015-10-27 (7 days ago)