src_prepare() { _python_rewrite_shebangs . } There's no such function. And even if there were, it would be internal. I have no idea what you're trying to do there but just don't.
note that this was removed in 0.16.6. I guess someone just forgot to drop it from older release.
+ 13 Sep 2013; Gilles Dartiguelongue <eva@gentoo.org> + -telepathy-gabble-0.16.4.ebuild: + Clean up old revision, bug #484402. + And now it's gone. Thanks for reporting.