buildpack can't complete if Gemfile.lock contains newer bundler version than the provided default version for the ruby version

[EverybodyKurts]

My gemfile specifies using ruby 2.6.3 and my Gemfile.lock specifies that it's bundled with version 2.0.2. Bundler version 2.0.1 is the one that comes with ruby 2.6.3.

Unfortuationely buildpack test will fail because of this, with the following error message:

-----> Installing node-v10.14.1-linux-x64
-----> Installing yarn-v1.12.3
-----> Detecting rake tasks

       !
       !     Could not detect rake tasks
       !     ensure you can run `$ bundle exec rake -P` against your app
       !     and using the production group of your Gemfile.
       !     Activating bundler (2.0.2) failed:
       !     Could not find 'bundler' (2.0.2) required by your /tmp/build/Gemfile.lock.
       !     To update to the latest version installed on your system, run `bundle update --bundler`.
       !     To install the missing version, run `gem install bundler:2.0.2`
       !     Checked in 'GEM_PATH=/tmp/build/vendor/bundle/ruby/2.6.0', execute `gem env` for more information
       !
       !     To install the version of bundler this project requires, run `gem install bundler -v '2.0.2'`
       !
/tmp/buildpacks/01_buildpack-ruby/lib/language_pack/helpers/rake_runner.rb:106:in `load_rake_tasks!': Could not detect rake tasks (LanguagePack::Helpers::RakeRunner::CannotLoadRakefileError)
ensure you can run `$ bundle exec rake -P` against your app
and using the production group of your Gemfile.
Activating bundler (2.0.2) failed:
Could not find 'bundler' (2.0.2) required by your /tmp/build/Gemfile.lock.
To update to the latest version installed on your system, run `bundle update --bundler`.
To install the missing version, run `gem install bundler:2.0.2`
Checked in 'GEM_PATH=/tmp/build/vendor/bundle/ruby/2.6.0', execute `gem env` for more information

To install the version of bundler this project requires, run `gem install bundler -v '2.0.2'`

[josegonzalez]

Thats an issue with the buildpack, not with this repository. Worth trying to replicate on heroku's CI platform and opening an issue upstream.