VOL-253: Initial commit for pkt-in/pkt-out for Edgecore adapter

- Add protobuf msg for pkt_send
- Implement pkt-in/pkt-out in adapter (untested)
- Misc changes to conform with pep8

Change-Id: I991b8e03a39b82524e0d9a9437765b3fe0c18529
diff --git a/voltha/adapters/device_handler.py b/voltha/adapters/device_handler.py
index 15f11eb..a952aa2 100644
--- a/voltha/adapters/device_handler.py
+++ b/voltha/adapters/device_handler.py
@@ -18,6 +18,7 @@
 from voltha.registry import registry
 from voltha.protos.common_pb2 import OperStatus, ConnectStatus, AdminState
 
+
 class DeviceHandler(object):
     def __init__(self, adapter, device_id):
         self.adapter = adapter
@@ -40,6 +41,7 @@
         device.connect_status = ConnectStatus.UNREACHABLE
         self.adapter_agent.update_device(device)
 
+
 class OltDeviceHandler(DeviceHandler):
     def __init__(self, adapter, device_id):
         super(OltDeviceHandler, self).__init__(adapter, device_id)
@@ -130,5 +132,9 @@
                 self.alarms.send_alarm(self, raw_data)
             '''
 
+    def packet_out(self, egress_port, msg):
+        raise NotImplementedError()
+
+
 class OnuDeviceHandler(DeviceHandler):
     pass