Unfortunately the host backing blackhole.snakebite.net and whitehole.snakebite.net is no longer available.  I still think the underlying test is valuable, though -- are there any PSF boxes/containers that could fulfill this role?

(I used pf on FreeBSD to set up the two firewall rules: https://github.com/python/cpython/blob/master/Lib/test/test_timeout.py#L183.  If a new box were to be sourced I presume it would be a Linux instance, so the rules would need to be ported to whatever the Linux firewall on the box is.)