How to solve the “undefined method `deep_symbolize_keys’ for nil:NilClass” error in Rails

I was trying to migrate a table in my Rails app and got this error: undefined method `deep_symbolize_keys’ for nil:NilClass It’s a strange error, and there weren’t very many hits on Google. A lighthouse ticket provided a clue. The problem wasn’t one of my plugins or gems — it was i18n itself. Upgrading from 0.4.1 […]