usb-control: print notice if run into langid error

listing boards can run into a permission problem.

Traceback (most recent call last):
  File "./haikou.py", line 49, in <module>
    product=PRODUCT_STRING, find_all=True))
  File "/usr/lib/python2.7/dist-packages/usb/core.py", line 1249, in device_iter
    if _interop._all(tests) and (custom_match is None or custom_match(d)):
  File "/usr/lib/python2.7/dist-packages/usb/core.py", line 1248, in <genexpr>
    tests = (val == getattr(d, key) for key, val in kwargs.items())
  File "/usr/lib/python2.7/dist-packages/usb/core.py", line 841, in product
    self._product = util.get_string(self, self.iProduct)
  File "/usr/lib/python2.7/dist-packages/usb/util.py", line 314, in get_string
    raise ValueError("The device has no langid")
ValueError: The device has no langid

catch the langid error and print a message that this could be a permission
problem. also link to the pyusb ticket https://github.com/walac/pyusb/issues/139

1 files changed, 9 insertions, 2 deletions

diff --git a/usb-control/haikou.py b/usb-control/haikou.py
index eb49eb4..15beb76 100755
--- a/usb-control/haikou.py
+++ b/usb-control/haikou.py
@@ -51,8 +51,15 @@ if not args.list and not args.power and not args.bios_disable \
         sys.exit()
 
 if args.list:
-        dev = list(usb.core.find(idVendor=VENDOR_ID, idProduct=PRODUCT_ID, \
-                product=PRODUCT_STRING, find_all=True))
+        try:
+            dev = list(usb.core.find(idVendor=VENDOR_ID, idProduct=PRODUCT_ID, \
+                    product=PRODUCT_STRING, find_all=True))
+
+        except ValueError, e:
+            if 'langid' in e.message:
+                raise usb.core.USBError(e.message + "\n" +
+                        "This may be a permission issue. See: \n"+
+                        "https://github.com/walac/pyusb/issues/139")
         print "Found %d Baseboard%s:" % (len(dev),"s"[len(dev)==1:])
         for idx,cfg in enumerate(dev):
                 print "%d: %s" % (idx, cfg.serial_number)