Comment 1 for bug 718390

Turns out to be an eventlet problem.

Eventlet monkey patches os, so that wait is called with the NOHANG flag in the standard python subprocess module, but it wasn't built for that, so if the timing is right, we'll call wait before the child has terminated, and then it never gets reaped. The solution is to use eventlet's subprocess module instead, but that's broken for us: https://bitbucket.org/which_linden/eventlet/issue/77/subprocess-module-fails-if-os-module-is