no such file to load -- ftools
<internal:lib/rubygems/custom_require>:29:in `require': no such file to load -- ftools (LoadError)
from <internal:lib/rubygems/custom_require>:29:in `require'
from ./configure.rb:62:in `<main>'


这是什么问题啊，求解，求答案。谢谢

[解决办法]
#gem install ftool