python3-checkbox-ng uninstallable on Ubuntu 12.04

[Daniel Manrique]

I was trying to install checkbox-ng and assorted friend utilities but couldn't. I traced it down to this:

$ sudo apt-get install python3-checkbox-ng
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 python3-checkbox-ng : Depends: python3:any (>= 3.2) but it is not installable
E: Unable to correct problems, you have held broken packages.

python3 (actually 3.2) does exist in 12.04, but that :any specification looks weird. It comes from the packaging branch:

Package: python3-checkbox-ng
Architecture: all
Depends:
 ${misc:Depends},
 python3-checkbox-support (>= 0.2),
 python3-plainbox (>= 0.5.3),
 python3-requests (>= 1.0),
 python3-xlsxwriter,
 python3:any (>= 3.2),
 ^^^^^^^^^^ notice here.

On Ubuntu 12.04, python3 is arch: all:

$ apt-cache show python3
Package: python3
Priority: optional
Section: python
Installed-Size: 206
Maintainer: Ubuntu Developers <email address hidden>
Original-Maintainer: Matthias Klose <email address hidden>
Architecture: all
Source: python3-defaults
Version: 3.2.3-0ubuntu1

While on e.g. 14.04, it's arch-specific (which I guess meets the arch:any restriction):

$ apt-cache show python3
Package: python3
Priority: important
Section: python
Installed-Size: 100
Maintainer: Ubuntu Developers <email address hidden>
Original-Maintainer: Matthias Klose <email address hidden>
Architecture: amd64
Source: python3-defaults
Version: 3.4.0-0ubuntu2