Hi there,
At this time, we're unable to include the full error message in our emails. So, the best way to see the full error associated with the failed build is to build your site locally using Jekyll and the github-pages gem:
https://help.github.com/articles/setting-up-your-github-pages-site-locally-with-jekyll
Here's the full error message I'm seeing on our end:
Liquid Exception: undefined method `to_liquid' for :auto_ids:Symbol in assets/css/main.scss
Fatal: NoMethodError
undefined method `to_liquid' for :auto_ids:Symbol
We recently updated Jekyll to a version that included a large update in Liquid to version 4.0.0. Your best option for debugging is to build your site locally to resolve this issue.