Merge pull request #61 from HarkonenBade/support-for-libusb0

Prevent crash when using libusb0 printers

escpos/printer.py

@@ -40,11 +40,19 @@ class Usb(Escpos):
         if self.device is None:
             print "Cable isn't plugged in"
 
-        if self.device.is_kernel_driver_active(0):
+        check_driver = None
+
+        try:
+            check_driver = self.device.is_kernel_driver_active(0)
+        except NotImplementedError:
+            pass
+
+        if check_driver is None or check_driver:
             try:
                 self.device.detach_kernel_driver(0)
             except usb.core.USBError as e:
-                print "Could not detatch kernel driver: %s" % str(e)
+                if check_driver is not None:
+                    print "Could not detatch kernel driver: %s" % str(e)
 
         try:
             self.device.set_configuration()