railsコマンドが急に起動しなくなった。 $ rails c /opt/local/lib/ruby1.9/gems/1.9.1/gems/thor-0.14.6/lib/thor/ base.rb:407:in `class_eval': No such file or directory - getcwd (Errno::ENOENT) from /opt/local/lib/ruby1.9/gems/1.9.1/gems/thor-0.14.6/lib/ thor/base.rb:91:in `register_klass_file' from /opt/local/lib/ruby1.9/gems/1.9.1/gems/thor-0.14.6/lib/ thor/base.rb:531:in `method_added' from (eval):1:in `block in pu