Linux: better error handling when USB permissions problem

[doegox]

On Linux, if someone forgets to install or update his /etc/udev/rules.d/99-newae.rules to include the ballisticgel VID:PID (hey what did you expect? ;) ), the python script fails with:

ValueError: The device has no langid

The error is not really helpful for someone to understand the root of the problem and the solution.
Example:

--- a/ballisticgel/naeusb.py
+++ b/ballisticgel/naeusb.py
@@ -109,7 +109,10 @@ class NAEUSB(object):
         """
 
         devlist = self.get_possible_devices(idProduct)
-        snlist = [d.serial_number + " (" + d.product + ")\n" for d in devlist]
+        try:
+            snlist = [d.serial_number + " (" + d.product + ")\n" for d in devlist]
+        except ValueError:
+            raise IOError("Check permissions to access the USB device")
         snlist = "".join(snlist)
 

$ 
python ballisticgel.py 
 CW521 Ballistic Gel Example Script 
  by NewAE Technology Inc
 This script will continue until you exit with Ctrl-C
Traceback (most recent call last):
  File "ballisticgel.py", line 306, in <module>
    cw521.con()
  File "ballisticgel.py", line 51, in con
    self.usb.con(idProduct=[usb_pid])
  File "/home/qb/00hardware_guilde/haqerspace/tools/chipshouter/ChipSHOUTER/ChipSHOUTER-ballisticgel/ballisticgel/naeusb.py", line 115, in con
    raise IOError("Check permissions to access the USB device")
IOError: Check permissions to access the USB device