Ensure bundler is pinned to version less than 2.0.0 on older rubies

travis/.travis.yml

@@ -5,9 +5,7 @@ cache:
   directories:
     - ../bundle
 before_install:
-  # We need to ensure the latest version of Rubygems, unless we're on an old Ruby.
-  - gem update --system $(ruby -e "puts '2.7.8' if ENV['RUBY_VERSION'] >= '2.3.0'")
-  - gem install bundler
+  - "script/update_rubygems_and_install_bundler"
   - unset _JAVA_OPTIONS
   - "script/clone_all_rspec_repos"
 bundler_args: "--binstubs --standalone --without documentation --path ../bundle"

travis/script/predicate_functions.sh

@@ -54,6 +54,14 @@ function is_mri_2plus {
   fi
 }
 
+function is_ruby_23_plus {
+  if ruby -e "exit(RUBY_VERSION.to_f >= 2.3)"; then
+    return 0
+  else
+    return 1
+  fi
+}
+
 function rspec_support_compatible {
   if [ "$MAINTENANCE_BRANCH" != "2-99-maintenance" ] && [ "$MAINTENANCE_BRANCH" != "2-14-maintenance" ]; then
     return 0

travis/script/update_rubygems_and_install_bundler

@@ -0,0 +1,12 @@
+#!/bin/bash
+set -e
+source script/functions.sh
+
+if is_ruby_23_plus; then
+  gem update --system
+  gem install bundler
+else
+  echo "Warning installing older versions of Rubygems / Bundler"
+  gem update --system '2.7.8'
+  gem install bundler -v '1.17.3'
+fi