This happened only for languages other than "en" and when `I18n.t` was called without any interpolation keys. The lib still tried to interpolate keys because it interpreted the `overrides` option as interpolation key.
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.