My project is extending open-source classes from a third-party gem that we don\'t want to hold to the same coding standards as our own code. Refactoring the gem code isn\'t
As per orde's comment with the link to the manual I found .rubocop.yml and added the following:
AllCops: Exclude: - 'path/to/excluded/file.rb'
where the path is relative to .rubocop.yml