Older macOS on Travis are not able to install Ruby 2.4.0

Author: ignisf

.travis.yml

@@ -12,7 +12,7 @@ matrix:
     - rvm: 2.4.0
       os: osx
       osx_image: xcode7.3
-    - rvm: 2.4.0
+    - rvm: 2.0.0
       os: osx
       osx_image: xcode6.4
     - rvm: 2.4.0
@@ -45,7 +45,8 @@ addons:
 bundler_args: --jobs=4 --retry=3
 before_install:
   - if [ "$TRAVIS_OS_NAME" == "linux" ]; then gem update bundler; fi
-  - if [ "$TRAVIS_OS_NAME" == "linux" ]; then gem update --system; fi
+  - if [ "$TRAVIS_OS_NAME" == "linux" ]; then gem update --system; f
+  - if [ "$TRAVIS_OS_NAME" == "osx" -a "$TRAVIS_RUBY_VERSION" == "2.0.0" ]; then rvm rubygems current; fi
   - if [ "$TRAVIS_OS_NAME" == "osx" -a "$TRAVIS_RUBY_VERSION" == "system" ]; then sudo gem install bundler; fi
   - if [ "$TRAVIS_OS_NAME" == "osx" -a "$TRAVIS_RUBY_VERSION" != "system" ]; then gem update --system; fi
   - if [ "$TRAVIS_OS_NAME" == "osx" -a "$TRAVIS_RUBY_VERSION" != "system" ]; then gem update bundler; fi