sudo: false
language: ruby
rvm:
  - 2.6.1
  - 2.5.3
gemfile:
  - gemfiles/rails_5.1.gemfile
  - gemfiles/rails_5.2.gemfile
before_install: gem install bundler -v 1.17.1

sudo: false
language: ruby
rvm:
  - 2.6.1
  - 2.5.3
gemfile:
  - gemfiles/rails_5.1.gemfile
  - gemfiles/rails_5.2.gemfile

Use bundled version of bundler
Use bundled version of bundler
