.travis.yml in ikazuchi-1.2.0 vs .travis.yml in ikazuchi-1.2.1

@@ -1,10 +1,12 @@
 language: ruby
-sudo: false
 cache: bundler
 rvm:
-  - 2.3.6
-  - 2.4.3
-  - 2.5.0
+  - 2.4.6
+  - 2.5.5
+  - 2.6.3
+before_install:
+  - gem uninstall -v '>= 2' -i $(rvm gemdir)@global -ax bundler || true
+  - gem install bundler -v '< 2'
 script:
   - bundle exec rubocop
   - bundle exec rake spec