Update inputs in scripts

scripts/openmc-get-photon-data

@@ -6,7 +6,6 @@ relaxation data and convert it to an HDF5 library for use with OpenMC.
 This data is used for photon transport in OpenMC.
 """
 
-from __future__ import print_function
 import os
 import sys
 import shutil

scripts/openmc-make-compton

@@ -1,12 +1,10 @@
 #!/usr/bin/env python
 
-from __future__ import print_function, division
 import os
 import sys
 import tarfile
+from urllib.request import urlopen
 
-from six.moves import input
-from six.moves.urllib.request import urlopen
 import numpy as np
 import h5py
 

scripts/openmc-make-stopping-powers

@@ -1,13 +1,11 @@
 #!/usr/bin/env python
 
-from __future__ import print_function
-
-from six.moves.urllib.parse import urlencode
-from six.moves.urllib.request import urlopen
+from urllib.parse import urlencode
+from urllib.request import urlopen
 from lxml import html
+
 import numpy as np
 import h5py
-
 from openmc.data import ATOMIC_SYMBOL