dev-python/pygtksourceview during configuration fails to find codegen if dev-lang/python-2.7 is set as default. Perhaps time to find a newer version?
Perhaps it's time to run python-updater ?
(In reply to comment #1) > Perhaps it's time to run python-updater ? That will be the next thing to do, once I've got all the packages built on this unstable x86 box (for testing purposes)
python-updater resolved the problem, consider this closed.