Ruby 备份gem的问题

我刚刚安装了gem备份。当我尝试一些东西时，我得到了这个错误。我能知道这是什么吗

$ backup
/usr/lib/ruby/gems/1.8/gems/backup-3.0.23/lib/backup/cli/utility.rb:240: warning:    parenthesize argument(s) for future version
/usr/lib/ruby/gems/1.8/gems/backup-3.0.23/lib/backup/cli/utility.rb:104: wrong argument type Symbol (expected Proc) (TypeError)
from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:29:in `gem_original_require'
from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:29:in `require'
from /usr/lib/ruby/gems/1.8/gems/backup-3.0.23/bin/backup:8
from /usr/bin/backup:19:in `load'
from /usr/bin/backup:19.


$ gem -v
1.4.0


gem list backup
*** LOCAL GEMS ***
backup (3.0.23)

ruby -v
ruby 1.8.6 (2007-09-24 patchlevel 111) [i686-linux]

---

浏览完备份gem文档后，我注意到ruby支持的最低版本是1.8.7。

您能提供一个生成此错误的代码行示例吗？