vpp_papi: Adjust aenum import for python3.

The stdlib introduced IntEnum in python 3.4 and IntFlag in python 3.6.

Change-Id: I3ac278a9d5a97eefa9fc4f1491f0cd030e40c3b2
Signed-off-by: Paul Vinciguerra <pvinci@vinciconsulting.com>

src/vpp-api/python/setup.py

@@ -13,7 +13,7 @@
 # limitations under the License.
 import sys
 
-stdlib_enum = sys.version_info >= (3, 4)
+stdlib_enum = sys.version_info >= (3, 6)
 
 try:
     from setuptools import setup, find_packages

src/vpp-api/python/vpp_papi/vpp_serializer.py

@@ -16,10 +16,17 @@
 import struct
 import collections
 import sys
-if sys.version[0] == '2':
-from aenum import IntEnum, IntFlag
+
+if sys.version_info <= (3, 4):
+    from aenum import IntEnum
 else:
-from enum import IntEnum, IntFlag
+from enum import IntEnum
+
+if sys.version_info <= (3, 6):
+    from aenum import IntFlag
+else:
+    from enum import IntFlag
+
 import logging
 from . import vpp_format
 import ipaddress

test/requirements.txt

@@ -1,3 +1,4 @@
+aenum>= 2.1.2; python_version < '3.6'   # BSD
 cffi                                    # MIT
 cryptography!=2.0                       # BSD/Apache-2.0
 faulthandler; python_version < '3.3' #  # BSD License (2 clause)