VPP-1508 Python3 abstract classes

Update the syntax to support abstract classes in python 2 and python 3.

Depends on: new style classes -- https://gerrit.fd.io/r/16166

Change-Id: Iad2c1240149f38b3faca1b37ab95d3d210e1daee
Signed-off-by: Paul Vinciguerra <pvinci@vinciconsulting.com>

test/util.py

@@ -1,9 +1,10 @@
 """ test framework utilities """
 
+import abc
 import socket
+import six
 import sys
 import os.path
-from abc import abstractmethod, ABCMeta
 from scapy.utils6 import in6_mactoifaceid
 
 from scapy.layers.l2 import Ether
@@ -93,11 +94,9 @@ def check_core_path(logger, core_path):
 
 
 class NumericConstant(object):
-    __metaclass__ = ABCMeta
 
     desc_dict = {}
 
-    @abstractmethod
     def __init__(self, value):
         self._value = value