Make sure bundler 2 is not installed

amatsuda · amatsuda · commit 6009197b7ef9 · 2019-05-20T21:14:48.000+09:00
or the CI fails on rubies 2.4.6 and 2.5.5
diff --git a/.travis.yml b/.travis.yml
@@ -5,6 +5,7 @@ cache:
   bundler: true
 
 before_install:
+  - gem uninstall -v '>= 2' -i $(rvm gemdir)@global -ax bundler || true
   - gem install bundler -v '< 2'
 
 rvm:
