When building scipy from the current portage tree, the source of scipy references the file qhull/qhull.h. But, alas, equery proves it not to be part of media-libs/qhull any more
# equery files media-libs/qhull | grep qhull.h /usr/include/libqhull/libqhull.h /usr/include/libqhull/qh-qhull.htm /usr/share/doc/qhull-2012.1-r1/html/qhull.htm
The good news: it's a known bug. The bad news: the only solution in case you want scipy to work now (as everything was due to yesterday...) is to unmask scipy. Please keep in mind that the following line is applicable for x86 architecture only.
# echo 'sci-libs/scipy ~x86' >> /etc/portage/package.keywords
Don't even think about blaming me for any scipy related compiling issues you are looking forward to by now ;)