bottle: detail what a new regex should match.

Library/Homebrew/cmd/bottle.rb

@@ -122,7 +122,7 @@ module Homebrew extend self
     filename = bottle_filename(f, :tag => bottle_tag, :revision => bottle_revision)
 
     if bottle_filename_formula_name(filename).empty?
-      return ofail "Add a new regex to bottle_version.rb to parse the bottle filename."
+      return ofail "Add a new regex to bottle_version.rb to parse #{f.version} from #{filename}"
     end
 
     bottle_path = Pathname.pwd/filename