Feature #17121
Updated by S_H_ (Shun Hiraoka) over 4 years ago
`ENV#index` is deprecated since `ruby-1.9.0-0`.
So, remove it.
```bash
root@8785b339158a:/all-ruby# env ALL_RUBY_SINCE=ruby-1.8 ./all-ruby -e 'ENV.index("RUBY")'
ruby-1.8.0
...
ruby-1.8.7-p374
ruby-1.9.0-0 -e:1: warning: ENV.index is deprecated; use ENV.key
...
ruby-2.7.0-rc1 -e:1: warning: ENV.index is deprecated; use ENV.key
ruby-2.7.0-rc2 -e:1: warning: ENV.index is deprecated; use ENV.key instead
...
ruby-2.7.1 -e:1: warning: ENV.index is deprecated; use ENV.key instead
```
pull request:
https://github.com/ruby/ruby/pull/3415