bundlerのVersionを固定して、実行する

問題

他の人が作ったライブラリーのspecを実行したときに、下記のエラーがでて困った。

$ bundle install

出力結果

Fetching gem metadata from https://rubygems.org/............
Fetching version metadata from https://rubygems.org/..
Resolving dependencies...
Bundler could not find compatible versions for gem "bundler":
  In Gemfile:
    bundler (~> 1.6.2) ruby

  Current Bundler version:
    bundler (1.9.9)
This Gemfile requires a different version of Bundler.
Perhaps you need to update Bundler by running `gem install bundler`?
Could not find gem 'bundler (~> 1.6.2) ruby in any of the sources

解決

$ gem install bundler -v '1.6.2'
$ bundle _1.6.2_ install

Rspec

$ bundle _1.6.2_  exec rspec ./spec