My Jekyll installation recently stopped working with following error when I tried to run
jekyll serve watch
WARN: Unresolved specs during Gem::Specification.reset: redcarpet ( > 3.1) jekyll-watch ( > 1.1) classifier-reborn ( > 2.0) WARN: Clearing out unresolved specs.
It would seem that there is an issue in one of the supporting gems. As a workaround you can use the following command if you installed jekyll via bundler
bunble exec jekyll serve
There’s a discussion of the issue here