mfg_gen: Add changes to make Python2 and Python3 compatible

tools/mass_mfg/mfg_gen.py

@@ -22,10 +22,9 @@ import csv
 import argparse
 import shutil
 import distutils.dir_util
+from itertools import zip_longest
 sys.path.insert(0, os.getenv('IDF_PATH') + "/components/nvs_flash/nvs_partition_generator/")
 import nvs_partition_gen
-if not sys.version_info[0] < 3:
-    from itertools import zip_longest
 
 def verify_values_exist(input_values_file, keys_in_values_file):
     """ Verify all keys have corresponding values in values file