use dict.items() instead of dict.iteritems() for Python 3

from: https://wiki.python.org/moin/Python3.0

> Remove dict.iteritems(), dict.iterkeys(), and dict.itervalues().
>    Instead: use dict.items(), dict.keys(), and dict.values() respectively.

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

Author: pdp7

test/test_led.py

@@ -34,7 +34,7 @@ def set_all_leds(self, state):
                       "USR1": "mmc0", \
                       "USR2": "cpu0", \
                       "USR3": "mmc1" }
-        for led, name in test_leds.iteritems():
+        for led, name in test_leds.items():
             self.set_brightness(state, led, name)
             GPIO.cleanup()