call

# File actionpack/lib/action_dispatch/middleware/show_exceptions.rb, line 45
    def call(env)
      begin
        status, headers, body = @app.call(env)
        exception = nil

        # Only this middleware cares about RoutingError. So, let's just raise
        # it here.
        if headers['X-Cascade'] == 'pass'
           raise ActionController::RoutingError, "No route matches #{env['PATH_INFO'].inspect}"
        end
      rescue Exception => exception
        raise exception if env['action_dispatch.show_exceptions'] == false
      end

      exception ? render_exception(env, exception) : [status, headers, body]
    end