The dependency on scalyr is documented in IntegrationRebuild.md but not InstallGuide.md.
The AMIs will not build without the existence of "boss-manage/salt-stack/pillar/scalyr.sls" and a valid scalyr api key.
I have not looked very deeply into salt yet, but we believe a preferable route would be to include a scalyr.sls with a setting along the lines of "use_scalyr: false".