The transaction allows to set a specific locale. Packagekitd uses this value to set the LANG env for spawned backends.
But on Debian/Ubuntu not all locale definitions of libc are shipped by default. They get generated from source by request.
If the daemon sets a not supported locale this will lead in a crash of a spawned python backend - which uses the locale settings for decoding stdin correctly.
This bug report is very old and based on a version not supported anymore. By upgrading to a newer version of PackageKit you could receive bug fixes and new functionality. You may need to upgrade your Linux distribution to obtain a newer version of PackageKit.
Please feel free to reopen this bug if the problem still occurs with the latest version.