今天打开程序，报下面这个错误
$ bundle install
You must use Bundler 2 or greater with this lockfile.
这个错误的原因的bundler插件版本过低，可能是因为某些gem更新了，所以我们来安装更高版本的bundler插件，这样错误就解决了
$ gem install bundler -v2.0.2
Fetching: bundler-2.0.2.gem (100%)
Successfully installed bundler-2.0.2
Parsing documentation for bundler-2.0.2
Installing ri documentation for bundler-2.0.2
Done installing documentation for bundler after 6 seconds
1 gem installed
