Developer of python-mode uses modified version, at least of ropemode, which is bundled with python-mode. Gentoo tries to use original ropemode instead. So now, 0.6.18-r1 have tons of errors with rope autocomplete.
Hacked ebuild in local overlay, now it works, but still barfs tons of errors in some situations (like trying to omni complete in empty line). Imma little bit frustrated. Now I understand why it masked.
+*python-mode-0.6.18-r2 (04 Jul 2013) + + 04 Jul 2013; Kacper Kowalik <xarthisius@gentoo.org> + +python-mode-0.6.18-r2.ebuild, -python-mode-0.6.18-r1.ebuild: + Use bundled rope wrt #475686 by neumond <knifeslaughter@gmail.com> Sorry for that :/ Those packages really needs to be debundled but it's hard to get it right. I've brought back rope* for the time being.