.travis.yml in active_model_cachers-2.1.5 vs .travis.yml in active_model_cachers-2.1.6

@@ -11,11 +11,11 @@
   - gemfiles/4.2.gemfile
   - gemfiles/5.0.gemfile
   - gemfiles/5.1.gemfile
   - gemfiles/5.2.gemfile
 before_install:
-  - gem install bundler
-  - gem update --system
+  - gem i rubygems-update -v '<3' && update_rubygems
+  - gem install bundler -v 1.17.3
   - gem --version
   - curl -L https://codeclimate.com/downloads/test-reporter/test-reporter-latest-linux-amd64 > ./cc-test-reporter
   - chmod +x ./cc-test-reporter
   - ./cc-test-reporter before-build
 script: