Merge pull request #249 from mulkieran/master-pyudev

Fix some bugs in udev.get_indexed_string.

lib/hidapi/udev.py

@@ -32,6 +32,7 @@ import os as _os
 import errno as _errno
 from select import select as _select
 from pyudev import Context as _Context, Monitor as _Monitor, Device as _Device
+from pyudev import DeviceNotFoundError
 
 
 native_implementation = 'udev'
@@ -338,14 +339,21 @@ def get_indexed_string(device_handle, index):
 
 	:param device_handle: a device handle returned by open() or open_path().
 	:param index: the index of the string to get.
+	:returns: the value corresponding to index, or None if no value found
+	:rtype: bytes or NoneType
 	"""
-	if index not in _DEVICE_STRINGS:
+	try:
+	    key = _DEVICE_STRINGS[index]
+	except KeyError:
 	    return None
 
 	assert device_handle
 	stat = _os.fstat(device_handle)
+	try:
 		dev = _Device.from_device_number(_Context(), 'char', stat.st_rdev)
-	if dev:
+	except (DeviceNotFoundError, ValueError):
+		return None
+
 	hid_dev = dev.find_parent('hid')
 	if hid_dev:
 		assert 'HID_ID' in hid_dev
@@ -354,10 +362,7 @@ def get_indexed_string(device_handle, index):
 		if bus == '0003':  # USB
 			usb_dev = dev.find_parent('usb', 'usb_device')
 			assert usb_dev
-				key = _DEVICE_STRINGS[index]
-				attrs = usb_dev.attributes
-				if key in attrs:
-					return attrs[key]
+			return usb_dev.attributes.get(key)
 
 		elif bus == '0005':  # BLUETOOTH
 			# TODO