class ActionDispatch::ShowExceptions

def call(env)
  @app.call(env)
rescue Exception => exception
  request = ActionDispatch::Request.new env
  backtrace_cleaner = request.get_header("action_dispatch.backtrace_cleaner")
  wrapper = ExceptionWrapper.new(backtrace_cleaner, exception)
  request.set_header "action_dispatch.exception", wrapper.unwrapped_exception
  request.set_header "action_dispatch.report_exception", !wrapper.rescue_response?
  if wrapper.show?(request)
    render_exception(request.dup, wrapper)
  else
    raise exception
  end
end