class RuboCop::Plugin::NotSupportedError

def initialize(unsupported_plugins)
  super
  @unsupported_plugins = unsupported_plugins
end

def message
  if @unsupported_plugins.one?
    about = @unsupported_plugins.first.about
    "#{about.name} #{about.version} is not a plugin supported by RuboCop engine."
  else
    unsupported_plugin_names = @unsupported_plugins.map do |plugin|
      "#{plugin.about.name} #{plugin.about.version}"
    end.join(', ')
    "#{unsupported_plugin_names} are not plugins supported by RuboCop engine."
  end
end