Bug#763576: ttf-cjk-compact: introduce error handling in the update script
as noted in  and in #762057, I was failing at updating this package,
getting broken fonts with Traditional Chinese as soon as I entered the
"Choose your location" prompt.
This is actually due to a wrong URL for the iso-codes package, which was
silently ignored, and leading to missing glyphs for Singapore, Taiwan,
and Hong Kong.
I'll be shortly addressing this particular URL issue in 1.23 but it
would be good to make sure any error is detected while updating, switch
URL to https, and maybe add other packages (like debian-edu stuff).
That's a topic for after D-I Jessie Beta 2 though.