Install the latest bundler
version:
gem install bundler
Fetching bundler-2.3.5.gem
Successfully installed bundler-2.3.5
1 gem installed
Update the bundler version in Gemfile.lock
:
bundle update --bundler
Confirm it worked:
$ tail -n2 Gemfile.lock
BUNDLED WITH
2.3.5
Bundler should automatically detect the latest installed version. If it does not, you can specify your preferred version like so:
bundle _2.1.2_ update --bundler
Older Ruby and Rails can not use the latest bundler 2 version, so you need to stay on bundler 1.