Pass sys.stdin.buffer to json.load() in Python 3

When running with Python 3 json.load() will only work with sys.stdin if
we pass there its buffer property. This commit implements that in
kuryr-cni.

Implements: blueprint goal-python36
Change-Id: Ic05f9071a792e30e56e002d9af61387a25eaa5c0
Closes-Bug: 1792191

kuryr_kubernetes/cni/main.py

@@ -15,6 +15,7 @@
 
 import os
 import signal
+import six
 import sys
 
 import os_vif
@@ -39,7 +40,11 @@ def run():
     # REVISIT(ivc): current CNI implementation provided by this package is
     # experimental and its primary purpose is to enable development of other
     # components (e.g. functional tests, service/LBaaSv2 support)
-    cni_conf = utils.CNIConfig(jsonutils.load(sys.stdin))
+    if six.PY3:
+        d = jsonutils.load(sys.stdin.buffer)
+    else:
+        d = jsonutils.load(sys.stdin)
+    cni_conf = utils.CNIConfig(d)
     args = ['--config-file', cni_conf.kuryr_conf]
 
     try: