#!/usr/bin/python
import RPi.GPIO as GPIO
import time
import subprocess

GPIO.setmode(GPIO.BOARD)
# set pin 16 to input, and enable the internal pull-up resistor
GPIO.setup(16, GPIO.IN, pull_up_down=GPIO.PUD_UP)

oldButtonState1 = True
while True:
   buttonState1 = GPIO.input(16)

    if buttonState1 != oldButtonState1 and buttonState1 == False :
        # print "Button 1 pressed"
        subprocess.call("halt", shell=True, stdout=subprocess.PIPE, stderr=subp$

    oldButtonState1 = buttonState1

    time.sleep(.1)

---------------------------------
RETURNS
---------------------------------
pi@raspberrypi2-no2:~$ sudo python haltButton.py
Traceback (most recent call last):
  File "haltButton.py", line 2, in <module>
    import RPi.GPIO as GPIO
RuntimeError: This module can only be run on a Raspberry Pi!