Setting PackageKit Catalog Installer as default application to open PackageKit Catalog file
In Fedora at least, the .catalog file is not properly set to be opened with PackageKit Catalog Installer. I have filed a bug report here : #770019.
In the meantime, you can set your system manually by creating ~/.local/share/applications/defaults.list with this content:
[Default Applications] application/x-catalog=gpk-install-catalog.desktop;