diff --git a/Generators/Herwig7_i/python/Herwig7Config.py b/Generators/Herwig7_i/python/Herwig7Config.py
index 58905a9246f593f8ca91c7f0e4bf9a5307292af3..71723c4d65d5ae9c59e38bfa97973aff70e10cb6 100644
--- a/Generators/Herwig7_i/python/Herwig7Config.py
+++ b/Generators/Herwig7_i/python/Herwig7Config.py
@@ -3,7 +3,7 @@
 ## \file Herwig7Config.py
 ## \brief Python convenience snippets providing re-usable bits of settings for use in the jobOptions
 
-import Herwig7Utils as hw7Utils
+from . import Herwig7Utils as hw7Utils
 
 ## Configuration base class for %Herwig7
 class Hw7Config(object):
diff --git a/Generators/Herwig7_i/python/Herwig7ConfigBuiltinME.py b/Generators/Herwig7_i/python/Herwig7ConfigBuiltinME.py
index eb0942b173ccc5d177c01bcef4636c9b9d25f9e1..329d00e36c21f1952c6a212299ab000bf7fd32fb 100644
--- a/Generators/Herwig7_i/python/Herwig7ConfigBuiltinME.py
+++ b/Generators/Herwig7_i/python/Herwig7ConfigBuiltinME.py
@@ -4,9 +4,9 @@
 ## \brief Configuration class for built-in / "old-style" matrix elements
 ## \author Daniel Rauch (daniel.rauch@desy.de)
 
-import Herwig7Config as hw7Config
-import Herwig7Control as hw7Control
-import Herwig7Utils as hw7Utils
+from . import Herwig7Config as hw7Config
+from . import Herwig7Control as hw7Control
+from . import Herwig7Utils as hw7Utils
 
 
 ## Configuration class for built-in / "old-style" matrix elements
diff --git a/Generators/Herwig7_i/python/Herwig7Control.py b/Generators/Herwig7_i/python/Herwig7Control.py
index c736c8e131ef7d42ebf671d20a2d90c37f9bd303..d03f2f44891b25d9fb2503ab426d72981da517be 100644
--- a/Generators/Herwig7_i/python/Herwig7Control.py
+++ b/Generators/Herwig7_i/python/Herwig7Control.py
@@ -11,9 +11,10 @@
 ## in Herwig7_i/Herwig7.h and src/Herwig7.cxx.
 
 import datetime, os, shutil, subprocess, sys, time
+import six
 
-import Herwig7Config as hw7Config
-import Herwig7Utils as hw7Utils
+from . import Herwig7Config as hw7Config
+from . import Herwig7Utils as hw7Utils
 # import Herwig7Defaults as HwDefaults
 
 from AthenaCommon import Logging
@@ -355,7 +356,7 @@ def start_banner():
 
 def get_software_versions():
 
-  return(subprocess.check_output([herwig7_binary,'--version']).splitlines())
+  return(six.ensure_str(subprocess.check_output([herwig7_binary,'--version'])).splitlines())
   
 
 def get_infile_name(run_name="Herwig-Matchbox"):
diff --git a/Generators/Herwig7_i/python/Herwig7Utils.py b/Generators/Herwig7_i/python/Herwig7Utils.py
index 71a7b979cf1e317c211fc78d386e42ecca5687c8..1f021fbe2f48ca5ed0312542c3c2765d39aa9621 100644
--- a/Generators/Herwig7_i/python/Herwig7Utils.py
+++ b/Generators/Herwig7_i/python/Herwig7Utils.py
@@ -184,11 +184,11 @@ def humanize_bytes(bytes, precision=2):
   # http://code.activestate.com/recipes/577081-humanized-representation-of-a-number-of-bytes/
 
   abbrevs = (
-      (1<<50L, 'PiB'),
-      (1<<40L, 'TiB'),
-      (1<<30L, 'GiB'),
-      (1<<20L, 'MiB'),
-      (1<<10L, 'KiB'),
+      (1<<50, 'PiB'),
+      (1<<40, 'TiB'),
+      (1<<30, 'GiB'),
+      (1<<20, 'MiB'),
+      (1<<10, 'KiB'),
       (1, 'byte(s)')
   )
   if bytes == 1:
diff --git a/Generators/Herwig7_i/python/config.py b/Generators/Herwig7_i/python/config.py
index 3e6a31008f77ea2ec01d43436393de0e7062b433..685404255741115345a191cbc13382a9b901b405 100644
--- a/Generators/Herwig7_i/python/config.py
+++ b/Generators/Herwig7_i/python/config.py
@@ -1,10 +1,12 @@
-# Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 ## \file Herwig7_i/python/config.py
 ## \brief Python functions that are usable in the Herwig 7 jobOptions
 ## \author Daniel Rauch (daniel.rauch@desy.de)
 ##
 
+from __future__ import print_function
+
 ## Choose symmetric collider energy
 def energy_cmds(sqrts):
     "Set sqrts(s) in GeV"
@@ -486,4 +488,4 @@ if __name__ == "__main__":
     sqrts = 14000
     if len(sys.argv) > 1:
         sqrts = float(sys.argv[1])
-    print energy_cmds(sqrts)
+    print (energy_cmds(sqrts))