dev-python/mysql-python-1.2.5 should add pypy to PYTHON_COMPAT by default: PYTHON_COMPAT=( python{2_6,2_7} pypy ) It builds and runs out of the box. Source: https://bitbucket.org/pypy/compatibility/wiki/mysql-python (I can confirm that it works on x86 and amd64 at least)
*mysql-python-1.2.5-r1 (19 Dec 2014) 19 Dec 2014; Ian Delaney <idella4@gentoo.org> +mysql-python-1.2.5-r1.ebuild: revbump; drop py2.6 add pypy, fixes bug #529842 sorry for delay, don't remember seeing this before