$ make serve
jekyll serve
Configuration file: /tmp/gap-lesson/_config.yml
Source: /tmp/gap-lesson
Destination: /tmp/gap-lesson/_site
Incremental build: disabled. Enable with --incremental
Generating...
Liquid Exception: Could not find document 'aio.md' in tag 'link'. Make sure the document exists and the path is correct. in /_layouts/base.html
jekyll 3.7.3 | Error: Could not find document 'aio.md' in tag 'link'.
Make sure the document exists and the path is correct.
make: *** [Makefile:21: serve] Error 1
Could you add https://raw.githubusercontent.com/swcarpentry/lesson-example/gh-pages/aio.md to this repository?