codeclimate/codeclimate-rubocop

A Gem's requirements should be listed only once in a Gemfile.
### Example:
    # bad
    gem 'rubocop'
    gem 'rubocop'

    # bad
    group :development do
      gem 'rubocop'
    end

    group :test do
      gem 'rubocop'
    end

    # good
    group :development, :test do
      gem 'rubocop'
    end

    # good
    gem 'rubocop', groups: [:development, :test]