In Jekyll 3, pagination is deprecated. This post describes how to resolve the error: “Deprecation: You appear to have pagination turned on, but you haven’t included the jekyll-paginate gem. Ensure you have gems: [jekyll-paginate] in your configuration file.”

First, make sure you have the gem installed by typing in your terminal: gem install jekyll-paginate

Next, open _config.yml, add add the following line:

gems :
  - jekyll-paginate

Now, when you run jekyll serve or jekyll build the error message should no longer be there.