maybe try downgrading bundler?

maybe try downgrading bundler?

diff --git a/.travis.yml b/.travis.yml
index d1781da..3c2596f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -26,6 +26,9 @@ matrix:
 
 sudo: false
 
+before_install:
+  - gem install bundler -v '< 2' --conservative
+
 install: bundle install --without development --retry=3 --jobs=3
 
 script:

GitHub sha: 21733cc8