Fix some python2-isms in prep for python3

These ones should work in both versions so we don't have to do them as
part of a global change over.

Change-Id: I2177b329d385c50d706a50a750b6c115ea3ea7ae
diff --git a/y2017/control_loops/python/turret.py b/y2017/control_loops/python/turret.py
index e8829eb..c5e4269 100755
--- a/y2017/control_loops/python/turret.py
+++ b/y2017/control_loops/python/turret.py
@@ -201,7 +201,7 @@
     profile.SetGoal(goal[0, 0])
 
     U_last = numpy.matrix(numpy.zeros((1, 1)))
-    for i in xrange(iterations):
+    for i in range(iterations):
       observer_turret.Y = turret.Y
       observer_turret.CorrectObserver(U_last)