def method_missing(cmd, *args, &block)
      if cmd == :to_ary
        super
      elsif @rye_safe
        ex = Rye::CommandNotFound.new(cmd.to_s)
        raise ex unless @rye_exception_hook.has_key? ex.class
        @rye_exception_hook[Rye::CommandNotFound].call ex
      else
        if block.nil?
          run_command cmd, *args
        else
          ex = Rye::CommandNotFound.new(cmd.to_s)
          raise ex unless @rye_exception_hook.has_key? ex.class
        end
      end
    end
def method_missing(cmd, *args, &block)
      if cmd == :to_ary
        super
      elsif @rye_safe
        ex = Rye::CommandNotFound.new(cmd.to_s)
        raise ex unless @rye_exception_hook.has_key? ex.class
        @rye_exception_hook[Rye::CommandNotFound].call ex
      else
        if block.nil?
          run_command cmd, *args
        else
          ex = Rye::CommandNotFound.new(cmd.to_s)
          raise ex unless @rye_exception_hook.has_key? ex.class
        end
      end
    end
A handler for undefined commands.
 Raises Rye::CommandNotFound exception.