El Capitan で gem install mysql2 が文字化けでエラー

現象

> gem install mysql

Building native extensions.  This could take a while...
Successfully installed mysql2-0.4.3
Parsing documentation for mysql2-0.4.3
unable to convert "\xCA" from ASCII-8BIT to UTF-8 for /Library/Ruby/Gems/2.0.0/extensions/universal-darwin-15/2.0.0/mysql2-0.4.3/mysql2/mysql2.bundle, skipping
unable to convert "\xCA" from ASCII-8BIT to UTF-8 for lib/mysql2/mysql2.bundle, skipping
Installing ri documentation for mysql2-0.4.3
1 gem installed
``=

## 対処
oh-my-zshでの文字化けが原因だった。.zshrcの冒頭に以下を追加で解決。現在の環境変数はenvコマンドで確認。

```.zshrc
export LANG=ja_JP.UTF-8
export LC_CTYPE=UTF-8

参考

• oh-my-zshで文字化け - Qiita
• oh-my-zshで日本語が文字化けする時の対処 - 面白コンテンツ探求日記