How to show all asked-for Translation Strings in Rails?

Question

When Rails functions are asking for a translation (I18n.translate), I don't want to analyze their code in order to get the exact scopes etc.

How can I add a debug output into the console for every string that was asked for?

Examples:

I18n.t 'errors.messages.invalid', :scope => :active_record 
# Translation for 'activerecord.errors.messages.invalid' (not) found

label(:post, :title)
# Translation for 'activerecord.attributes.post.title' not found
# Translation for 'views.labels.post.title' not found