class MiniRacer::RuntimeError

def backtrace
  val = super
  return unless val
  if @js_backtrace
    @js_backtrace + val
  else
    val
  end
end

def initialize(message)
  message, js_backtrace = message.split("\n", 2)
  if js_backtrace && !js_backtrace.empty?
    @js_backtrace = js_backtrace.split("\n")
    @js_backtrace.map!{|f| "JavaScript #{f.strip}"}
  else
    @js_backtrace = nil
  end
  super(message)
end