The current one is "#!/usr/bin/python"; should be /usr/bin/python2 because bad things happen when python3 is eselected as the system default. Upstream seems dead unfortunately (and all the github clones of it have the same problem), otherwise I'd go badger them about it instead...
*pgtune-0.9.3-r1 (11 Nov 2012) 11 Nov 2012; <titan@gentoo.org> +pgtune-0.9.3-r1.ebuild: Explicit Python. Fixes bug 434054.