Add support for Python 3

DaVinciTests/tests/options/CommonParticles/DVTestStandardIntermediate.py

 ###############################################################################
-# (c) Copyright 2000-2018 CERN for the benefit of the LHCb Collaboration      #
+# (c) Copyright 2000-2020 CERN for the benefit of the LHCb Collaboration      #
 #                                                                             #
 # This software is distributed under the terms of the GNU General Public      #
 # Licence version 3 (GPL Version 3), copied verbatim in the file "COPYING".   #
@@ -16,6 +16,7 @@
 # Author: Patrick Koppenburg <patrick.koppenburg@cern.ch>
 #
 ##############################################################################
+from __future__ import print_function
 from DaVinci.Configuration import DaVinci
 from Gaudi.Configuration import *
 ##############################################################################
@@ -24,8 +25,8 @@ from CommonParticles import StandardBasic
 from CommonParticles import StandardIntermediate
 
 Locations = []
-for a,b in StandardIntermediate.locations.iteritems():
-    print "DVTestCommonParticles adding location", a
+for a,b in StandardIntermediate.locations.items():
+    print("DVTestCommonParticles adding location", a)
     Locations.append(a)
 
 from Configurables import CountParticles