On a pure Rack app that uses some Rails based middleware like Devise, Rails.logger can be defined, but nil. In that case, the safest behavior is probably to continue on until we return a new Logger to STDERR. This is especially true on Heroku where we will definitely end up in the rescue block.
When Exceptional is used in development mode and configured with ENV vars only, in development mode, above error message appears. Exceptional::Config.should_send_to_api? should be called before laoding the config file.