It works for me using this workaround:
- Set the version of bundler as an environment variable:
docker:
- image: circleci/ruby:2.6.0-node
environment:
BUNDLER_VERSION: 2.0.1
2 - Running these steps before bundle install
sudo gem update --system
sudo gem uninstall bundler
sudo rm /usr/local/bin/bundle
sudo rm /usr/local/bin/bundler
sudo gem install bundler
I guess the solution here is that circleci/ruby:2.6.0-node
image comes with Bundler 2 by default.