class ActiveAdmin::Dependency::Matcher

def <=>(other)
  if @spec
    @spec.version <=> Gem::Version.create(other)
  else
    # you'd otherwise get an unhelpful error message:
    # ArgumentError: comparison of ActiveAdmin::Dependency::Matcher with 2 failed
    raise DependencyError, "To use #{@name} you need to specify it in your Gemfile."
  end
end