By default we depend on py-gtk+2 except for the python3 FLAVOR where we depend
on py-gobject3 and gtk+3. We don't want to depend on all possible toolkits for
obvious reason, so people will have to manually install py-qt4 for example to
use the qt4 toolkit.
changes triggered by a mail from Predrag Punosevac
ok daniel@ (maintainer) who may revisit this port if needed in a few days
a00d2c6617