Fix : Weird exception would be raised after 'books.keys'
Fix : Weird exception would be raised after 'books.keys'

Signed-off-by: Steve Klabnik <9ce5770b3bb4b2a1d59be2d97e34379cd192299f@steveklabnik.com>
hacketyhack/hacketyhack,whymirror/hacketyhack,PragTob/hacketyhack,mvz/hacketyhack