И вот она - ошибка:
calculate roman # ebuild /usr/local/portage/sci-biology/gnaural-1.0.20110606/gnaural-1.0.20110606.ebuild digest
!!! /usr/local/portage/sci-biology/gnaural-1.0.20110606/gnaural-1.0.20110606.ebuild does not seem to have a valid PORTDIR structure.
И так со всеми ключами типа unpack, compile, install.