dev-python/nose-0.10.3 does not work with Python 2.6. See the upstream bug at http://code.google.com/p/python-nose/issues/detail?id=161 for details. The fix is in 0.10.4. Please upgrade nose to that version, so that Gentoo has a Python-2.6 compatible version of nose.
Thanks for the report, assigning bump request to maintainers
Thanks, added to CVS.