It's very easy to forget to add `require 'rails_helper'` at the top of every core/plugin spec file, and omissions can cause some very confusing/sporadic errors.
By setting this flag in `.rspec`, we can remove the need for `require 'rails_helper'` entirely.
Locale files get precompiled after deployment and they contained translations from the `default_locale`. That's especially bad in multisites, because the initial `default_locale` is `en_US`. Sites where the `default_locale` isn't `en_US` could see missing translations. The same thing could happen when users are allowed to chose a different locale.
This change simplifies the logic by not using the `default_locale` in the locale chain. It always falls back to `en` in case of missing translations.
Phil Pirozhkov
David Taylor
Gerhard Schlager