我跑了
gem uninstall rails -v 6.0.0.rc1
gem uninstall railties -v 6.0.0.rc1
甚至rvm remove ruby-2.6.1
然后重新安装ruby，创建了一个新的gemset，但是在任何bin/rails generate ..命令上（使用rails 5.2.3）都收到此错误：
Running via Spring preloader in process 25797
.rvm/gems/ruby-2.6.1/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require': cannot load such file -- /home/me/.rvm/gems/ruby-2.6.1/gems/railties-6.0.0.rc1/lib/rails/commands.rb (LoadError)