我正在尝试运行我刚刚创建的数据库迁移。Rake 以前工作得很好，我想我搞砸了依赖项或版本。这是我跑步时得到的。
rake:db:migrate --trace
rake aborted!
no such file to load -- rake/rdoctask
/var/lib/gems/1.8/gems/railties-3.0.7/lib/rails/tasks/documentation.rake:1:in `require'
/var/lib/gems/1.8/gems/railties-3.0.7/lib/rails/tasks/documentation.rake:1
/var/lib/gems/1.8/gems/railties-3.0.7/lib/rails/tasks.rb:15:in `load'
/var/lib/gems/1.8/gems/railties-3.0.7/lib/rails/tasks.rb:15
/var/lib/gems/1.8/gems/railties-3.0.7/lib/rails/tasks.rb:6:in `each'
/var/lib/gems/1.8/gems/railties-3.0.7/lib/rails/tasks.rb:6
/var/lib/gems/1.8/gems/railties-3.0.7/lib/rails/application.rb:214:in `require'
/var/lib/gems/1.8/gems/railties-3.0.7/lib/rails/application.rb:214:in `initialize_tasks'
/var/lib/gems/1.8/gems/railties-3.0.7/lib/rails/application.rb:139:in `load_tasks'
/var/lib/gems/1.8/gems/railties-3.0.7/lib/rails/application.rb:77:in `send'
/var/lib/gems/1.8/gems/railties-3.0.7/lib/rails/application.rb:77:in `method_missing'
/home/maaz/Desktop/rails_apps/todo/Rakefile:7
/var/lib/gems/1.8/gems/rake-10.0.2/lib/rake/rake_module.rb:25:in `load'
/var/lib/gems/1.8/gems/rake-10.0.2/lib/rake/rake_module.rb:25:in `load_rakefile'
/var/lib/gems/1.8/gems/rake-10.0.2/lib/rake/application.rb:581:in `raw_load_rakefile'
/var/lib/gems/1.8/gems/rake-10.0.2/lib/rake/application.rb:87:in `load_rakefile'
/var/lib/gems/1.8/gems/rake-10.0.2/lib/rake/application.rb:158:in `standard_exception_handling'
/var/lib/gems/1.8/gems/rake-10.0.2/lib/rake/application.rb:86:in `load_rakefile'
/var/lib/gems/1.8/gems/rake-10.0.2/lib/rake/application.rb:70:in `run'
/var/lib/gems/1.8/gems/rake-10.0.2/lib/rake/application.rb:158:in `standard_exception_handling'
/var/lib/gems/1.8/gems/rake-10.0.2/lib/rake/application.rb:68:in `run'
/var/lib/gems/1.8/gems/rake-10.0.2/bin/rake:37
/usr/local/bin/rake:19:in `load'
/usr/local/bin/rake:19