Intro

Mission: Debug failed github-pages site build (powered by JekyII).

Overview

Some times ago my site stopped updating process. I looked in my default github CI and found that JekyII couldnt build site. All what I got - message “Page build failed.” :)
So I thought that where should be some way to debug this problem!

Preparation

We need to install several ruby gems and stuff. I used my Ubuntu 18 VM for that purpose.
Disclaimer! It’s very important to use the same versions of all gems that github itself uses. For reference use this page - https://pages.github.com/versions/. I used this versions on some gems:

• jekyll-3.8.5;
• public_suffix-3.0;
• github-pages-204;

Install apt packages and ruby gems.
apt-get install ruby-full build-essential zlib1g-dev -y gem install jekyll -v 3.8.5 bundler
Create new temporary dir and initialize jekyII project.
jekyll new temp
Now copy your site from github
git clone github.com/myrepo
Move Gemfiles from temp directory to your project’s dir
mv temp/Gemfile* myrepo/
Update in Gemfile line with JekyII
vim myrepo/Gemfile #gem "jekyll", "~> 3.8.5" gem "github-pages", "~> 204", group: :jekyll_plugins #insert that line
Now run your site
bundle exec jekyll serve
You can encounter some errors due to different gem’s versions in Gemfile/Gemfile.lock, etc.. Resolve them locally (i.e. update Gemfile/lock, install required versions according to github-pages dep version page).
After that I got my error printed, nice and clear
Liquid Exception: Liquid error (line 260): wrong number of arguments (given 3, expected 2) in cheats.md
And in file cheats.md at line 260+6(header) I had this line:
msg: "\{\{ (groups['prometheus'] | map('extract', hostvars, ['custom_fact']) | join(',')).split(',') \}\}". Obviously, problem was in double curl braces with jinja syntax which JekyII was interpreted as Liquid syntax.
So I escaped these bracese, commited code to github and got successful build of my site.