class Rack::Lint::Wrapper

def verify_to_path
  ##
  ## If the Body responds to +to_path+, it must return a +String+
  ## path for the local file system whose contents are identical
  ## to that produced by calling +each+; this may be used by the
  ## server as an alternative, possibly more efficient way to
  ## transport the response. The +to_path+ method does not consume
  ## the body.
  if @body.respond_to?(:to_path)
    unless ::File.exist? @body.to_path
      raise LintError, "The file identified by body.to_path does not exist"
    end
  end
end