class Roadie::ProvidersFailed

def build_message(extra_message)
  message = +%(Could not find stylesheet "#{css_name}": #{extra_message}\nUsed providers:\n)
  each_error_row(errors) do |row|
    message << "\t" << row << "\n"
  end
  message
end

def each_error_row(errors)
  errors.each do |error|
    case error
    when ProvidersFailed
      each_error_row(error.errors) { |row| yield row }
    when CssNotFound
      yield error.error_row
    else
      yield "Unknown provider (#{error.class}): #{error}"
    end
  end
end

def initialize(css_name, provider_list, errors)
  @errors = errors
  super(css_name, "All providers failed", provider_list)
end