Added the following to my Vagrantfile and get further:
config.vm.provision :shell,
:inline => "sudo useradd vagrant; sudo adduser vagrant sudo"
But now get a new error:
Failed to upload a file to the guest VM via SCP due to a permissions
error. This is normally because the user running Vagrant doesn't have
read permission on the file. Please set proper permissions on the file:
/tmp/vagrant20130415-4687-8wl5cp