Hmm, I wonder if this is another race condition similar to issue 8458?

I think that was thought to be related to the subprocess exiting quickly, in which case the question might be why that might happen more so than the actual descriptor error.

BTW, Victor, in case it would help, your account (vstinner, ssh key haypo@marge) still exists on this buildbot from past testing in 2011.  The only thing I'd need to re-enable is the port forwarding on my firewall.