[Ruby on Rails 4] rails の bundle コマンドで bundler のバージョンエラーが出た場合の対処

チェックしたいプロジェクトでエラーが表示されたので暫定処置。

## 症状

`bundler (< 2.0, >= 1.3.0)` を要求されています。

“`prettyprinted
% bundle outdated
Bundler could not find compatible versions for gem “bundler”:
In Gemfile:
rails (= 4.2.11) was resolved to 4.2.11, which depends on
bundler (< 2.0, >= 1.3.0)

Current Bundler version:
bundler (2.0.2)
This Gemfile requires a different version of Bundler.
Perhaps you need to update Bundler by running `gem install bundler`?
“`

## 対処

こちらを参考に。

> – [ruby – Bundle install do not work for rails-4.2.6 for bundler 2.0.1 – Stack Overflow](https://stackoverflow.com/questions/55498245/bundle-install-do-not-work-for-rails-4-2-6-for-bundler-2-0-1)
> – [Installing Rails 4.2 with Bundler 2.0 fails · Issue #35518 · rails/rails](https://github.com/rails/rails/issues/35518)

bundler v1 系の最新版を確認すると v1.17.3 なのでインストールします。

> – [Tags · rubygems/bundler](https://github.com/rubygems/bundler/tags?after=v2.1.0.pre.1)

“`prettyprinted
% gem install bundler -v 1.17.3
“`

バージョンを指定して再実行。

“`prettyprinted
% bundle _1.17.3_ outdated
“`