The readme indicates that pcreate should be used. Scaffolds are deprecated in Pyramid 1.8a1.
https://docs.pylonsproject.org/projects/pyramid/en/latest/changes.html#a1-2016-12-25
The preferred alternative is https://github.com/Pylons/pyramid-cookiecutter-starter
I'm not sure what needs to be updated in code for this add-on, but I can at least submit a PR for updating the getting started bits.