An actual helpful error message

Wow, an exception error message that actually suggests a fix for the error, and the fix is correct. How great is that?

ActionController::RedirectBackError: No HTTP_REFERER was set in the request to this action, so redirect_to :back could not be called successfully. If this is a test, make sure to specify @request.env[“HTTP_REFERER”].

That sure beats “Unspecified error 0×0057867”.