Google Code-in

GTK+ 2 and GStreamer 0.10 are end of life.We need to upgrade the remaining activities with these dependencies.”, we need to upgrade the Sugar activities to maintain its support and get security update on various platforms. The movement from PyGTK to PyGObject API means no more maintenance of it. GTK+ 3 is a major new version of GTK+ that breaks both API and ABI compared to GTK+ 2, which has remained API- and ABI-stable for a long time.

See porting guide.

For background information check here.