new

# File actionpack/lib/action_dispatch/middleware/session/abstract_store.rb, line 12
      def initialize
        super("Session contains objects whose class definition isn't available.\n"            "Remember to require the classes for all objects kept in the session.\n"            "(Original exception: #{$!.message} [#{$!.class}])\n")
        set_backtrace $!.backtrace
      end