我想用ruby 1.8.7和rails 3.0.20为rails应用程序创建一个引擎，但是当我输入：
rails plugin new try --full
我明白了：
/Users/tborisova/.rvm/gems/ruby-1.8.7-p352/gems/railties-3.0.20/lib/rails/commands/plugin.rb:277: Commands is not a module (TypeError)
from /Users/tborisova/.rvm/gems/ruby-1.8.7-p352/gems/activesupport-3.0.20/lib/active_support/dependencies.rb:242:in `require'
from /Users/tborisova/.rvm/gems/ruby-1.8.7-p352/gems/activesupport-3.0.20/lib/active_support/dependencies.rb:242:in `require'
from /Users/tborisova/.rvm/gems/ruby-1.8.7-p352/gems/activesupport-3.0.20/lib/active_support/dependencies.rb:225:in `load_dependency'
from /Users/tborisova/.rvm/gems/ruby-1.8.7-p352/gems/activesupport-3.0.20/lib/active_support/dependencies.rb:597:in `new_constants_in'
from /Users/tborisova/.rvm/gems/ruby-1.8.7-p352/gems/activesupport-3.0.20/lib/active_support/dependencies.rb:225:in `load_dependency'
from /Users/tborisova/.rvm/gems/ruby-1.8.7-p352/gems/activesupport-3.0.20/lib/active_support/dependencies.rb:242:in `require'
from /Users/tborisova/.rvm/gems/ruby-1.8.7-p352/gems/railties-3.0.20/lib/rails/commands.rb:17
from script/rails:6:in `require'
from script/rails:6