Exclude bundler versions known to break build on 2.3

Author: JonRowe

travis/.travis.yml

@@ -5,8 +5,8 @@ cache:
     - ../bundle
 before_install:
   - "script/clone_all_rspec_repos"
-  # Note this doesn't work on JRUBY 2.0.0 mode so we don't do it
-  - if [ "jruby" != "$TRAVIS_RUBY_VERSION"  ]; then gem install bundler; fi
+  # Note this doesn't work on JRUBY 2.0.0 mode so we don't do it, the excluded versions are broken on Ruby 2.3
+  - if [ "jruby" != "$TRAVIS_RUBY_VERSION"  ]; then gem install bundler --version "!= 1.12.0, != 1.12.1"; fi
 bundler_args: "--binstubs --standalone --without documentation --path ../bundle"
 script: "script/run_build"
 rvm: