workaround for bundler-1.13.1

Author: hsbt

Rakefile

@@ -9,6 +9,10 @@
 lib = File.expand_path('../lib', __FILE__)
 $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 
+
+# XXX: https://github.com/bundler/bundler/pull/4981
+require 'bundler/plugin/api/source'
+
 require 'bundler/gem_tasks'
 require 'rake/testtask'
 require 'rdoc/task'

appveyor.yml

@@ -4,15 +4,13 @@ clone_depth: 10
 install:
   - SET PATH=C:\Ruby%ruby_version%\bin;%PATH%
   - ruby --version
-  - gem update --system
   - gem --version
-  - gem install minitest --no-document
+  - gem install minitest bundler --no-document
 build_script:
   - net user
   - net localgroup
 test_script:
   - ruby -Ilib exe/rake
-
 environment:
   matrix:
     - ruby_version: "193"