http://www.pyyaml.org/ seems to be down, and this prevents ruby-build from completing. Maybe there's a mirror you can use?
I agree, it would be nice if there were a mirror.
pyyaml.org is down (again? for the past 16 days?) Here is a mirror: http://pyyaml-mirror.gefira.pl/simple/
We are now mirroring all package files on S3: 093e390...e71a460