fix except syntax for Python 3

Signed-off-by: Drew Fustini <drew@pdp7.com>

Author: pdp7

test/test_led.py

@@ -25,7 +25,7 @@ def set_brightness(self, state, led, name):
     def read_led_file(self, path):
         try:
             return open(path).read()
-        except IOError, e:
+        except (IOError, e):
             if e.errno == errno.ENOENT:
                 return -1