ruby – update default bundler

Whenever I get this error, I have to again do a google search. So, this post is for me not to do that again!

Could not find 'bundler' (2.1.4) 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:2.1.4`

Unfortunately, the suggestions don’t quite work.

The correct way to fix this is to run these three commands:

gem install --default bundler
gem update --system
bundler update --bundler

Courtesy of StackOverflow. (The correct answer on StackOverflow didn’t quite work either!)