How to install bundler for Ruby < 2.3

You may get the following error when you attempt to install Bundler 2 with Ruby version < 2.3

ERROR:  Error installing bundler:
    bundler requires Ruby version >= 2.3.0.

In order to address this, we must update the ruby version of your project or set up the last supported Bundler version for Ruby < 2.3

gem install bundler -v '~>1'