This is related to bug 541948 The ebuild for sys-process/htop-1.0.3 pulls in Python 2 when it doesn't need it, and it also builds successfully if you change the .ebuild to depend on Python 3.4. It turns out that the only Python-related file in the distribution is the MakeHeader.py script (as mentioned in the aforementioned bug); however, the files that it generates are also included in the tarball, and so the script is never called. It seems silly to force people to install Python 2 when htop doesn't need it. Furthermore, it should only be a build-time dependency if you're going to keep it.
Ignore the last sentence; it already is build time.
*** Bug 541948 has been marked as a duplicate of this bug. ***
Thanks! It's indeed unneeded. I removed the python foo from 1.0.3-r1.