Comment 5 for bug 1290562

For reasons as of yet unidentified, pip is able to upgrade setuptools to 3.1 safely but if it tries to go any higher, that's when we hit this bug. Projects wishing to work around it temporarily without disabling PyPy testing can apply something along the lines of http://paste.openstack.org/show/73701/ to their tox.ini files while a proper fix is identified (whether that be in pip, setuptools, the PyPy interpreter or somewhere else entirely).