This worked for making the wheels spin

mappingbot/drive_test.py

+import RPi.GPIO as GPIO
+import time
+GPIO.setmode(GPIO.BCM)
+GPIO.setup(12, GPIO.OUT)
+GPIO.setup(20, GPIO.OUT)
+GPIO.setup(26, GPIO.OUT)
+GPIO.setup(13, GPIO.OUT)
+print(GPIO.VERSION)
+pRf = GPIO.PWM(20, 50)
+pRb = GPIO.PWM(26, 50)
+pLf = GPIO.PWM(12, 50)
+pLb = GPIO.PWM(13, 50)
+
+pRf.start(100)
+input("pRf")
+pRf.stop()
+pRb.start(100)
+input("pRb")
+pRb.stop()
+pLb.start(100)
+input("pLb")
+pLb.stop()
+pLf.start(100)
+input("pLf")
+pLf.stop()
+
+GPIO.cleanup()