$ bundle install
Could not find 'bundler' (2.0.2) required by your Gemfile.lock. (Gem::GemNotFoundException)
To update to the latest version installed on your system, run `bundle update --bundler`.
To install the missing version, run `gem install bundler:2.0.2`
$ bundle update --bundler
You must use Bundler 2 or greater with this lockfile.
笑えるw
$ gem install bundler
Fetching bundler-2.0.2.gem
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 3 seconds
1 gem installed
で解決