Python3 support
This branch includes a few of @bam 's fixes, plus a bunch of my own. So far it only adds py3 support, but it doesn't change any of the binaries. However I have been testing this branch with:
bin/check-syntax bin/update-db bin/apt-update-file bin/tracker_service.py
Under both python2 and python3, trying not to break python2 but getting farther with python3 in every single commit. With the whole branch applied, all of those commands should run fine with both py2 and py3.
There's also some unrelated fixes here, such as the sorting one (tracker_service: properly sort fixed versions table).
My idea would be to give this more testing, possibly fix a few more py3 incompatibilities if any arise, and get it merged and deployed. Then after that, start moving binaries to py3 (with proper testing, and fixing any extra incompatibilities that they raise) until we have everything (particularly the core/service parts) ported. Some time after that we could remove any code relating to the py2 support.