A man without a country (or language)

[Buddlespit]

Well, it's fixed. I uninstalled localepurge, then reinstalled kde-runtime-data and kdelibs5-data:

$ sudo apt-get uninstall --purge localepurge
$ sudo apt-get install --reinstall kdelibs5-data
$ sudo apt-get install --reinstall kde-runtime-data

[SteveRiley]

Yep, that does work. Harald gave my bug some love, and we now know why these files were missing from our systems. I reinstalled localepurge, and so far it hasn't touched the files that previously got deleted.