Bug#904320: ease backporting

[Lumin]

Hi Daniel,

> How about only generating the files when creating the source package,
> rather than during every build. that way, you would need to run it only
> before uploading the package, once; and none of the buildds would run it
> again which would also make the package a bit more resiliant.

Sorry but no, I won't keep any automatically-generated files in the
source tarball. And the file generator control.py generates different
files for amd64 and i386.

However, if you are willing to port it back to stretch, I can port
control.py to python3.5 .