Error message for key not found when the key is a string now shows the string value that was used.
Error message for key not found when the key is a string now shows the string value that was used.

------------------------------
Imported from Google Code.
Original SVN rev#: 283

blakeohare/crayon,blakeohare/crayon,blakeohare/crayon,blakeohare/crayon,blakeohare/crayon,blakeohare/crayon,blakeohare/crayon,blakeohare/crayon