Auto DevOps requires Bundler version 2.0.1

Currently, an arbitrary Rails app cannot be deployed using Auto DevOps. It's likely that some combination of ruby, rails, bundler, postgres client and devise gem will work, but this is not documented anywhere that I could find.

Here are the pipeline failures I've been getting: https://gitlab.com/devin/license-gitlab-com/pipelines

bundler

The Buildpack constructs an environment with bundler 2.0.1, so if the Gemfile and Gemfile.lock use a different version, the pod will fail with an error about bundler versioning in the Kubernetes logs.

The failure is not easy to diagnose using the job output: https://gitlab.com/devin/license-gitlab-com/-/jobs/218385745