FYI, Generate Cover included:
Code:
from calibre.gui2 import NONE
# ... which trunk calibre/gui2/__init__.py defines as:
NONE = QVariant() # : Null value to return from the data function of item models
NONE is used to return when font family isn't found or something like that. I'm not sure what it's doing with a cursory look.
Changing NONE to u'' works with qt5, but not with qt4, so I kept the gui2 import when using qt4. Without it, the font family drop list in GC isn't populated.