But I get this error without explicitly requiring `i18n/tasks/base_task` 

```
     Failure/Error: let(:i18n) { I18n::Tasks::BaseTask.new }
     NameError:
       uninitialized constant I18n::Tasks::BaseTask
     # ./spec/i18n_en_spec.rb:6:in `block (2 levels) in <top (required)>'
     # ./spec/i18n_en_spec.rb:9:in `block (2 levels) in <top (required)>'
     # -e:1:in `<main>'
```