Problems with PyUSB in Python 2.7. Do I need LibUSB driver?

Question

I installed PyUSB from source for Python 2.7

When I import the module I get no error, but when I try:

printers = usb.core.find(find_all=True, bDeviceClass=7)

or

dev = usb.core.find(idVendor=0x04d8, idProduct=0x003f)

I get:

TypeError: expected string or Unicode object, NoneType found

I'm able to communicate correctly with this device in C#, and was curious why it doesn't appear in PyUSB.