ActiveRecord::Base::human_attribute_name was deprecated by DHH over two years ago in [773], but we didn't have a formal deprecation mechanism back then, and it's remained in use here and there across the AR codebase.
The method was deprecated in favor of just using the humanize inflector directly. I made this change in two places, and I put in a formal deprecation warning to go with DHH's original comment.
Note that without this method, we're left without a handy hook to change the way the attribute names get humanized. The cleanest way to solve this, I think, is to let us add custom inflections for humanize the same way we do for pluralize. There's a lovely, verified patch for this over in this neck of the woods: #6989.
