Bug 757174: Better error message when marionette can no longer communicate with Gecko. DONTBUILD because NPOTB r=jgriffin

testing/marionette/client/marionette/client.py

@@ -5,6 +5,8 @@
 import json
 import socket
 
+from errors import MarionetteException
+
 class MarionetteClient(object):
     """ The Marionette socket client.  This speaks the same protocol
         as the remote debugger inside Gecko, in which messages are
@@ -42,9 +44,12 @@ class MarionetteClient(object):
         response = self.sock.recv(10)
         sep = response.find(':')
         length = response[0:sep]
-        response = response[sep + 1:]
-        response += self._recv_n_bytes(int(length) + 1 + len(length) - 10)
-        return json.loads(response)
+        if length != '':
+            response = response[sep + 1:]
+            response += self._recv_n_bytes(int(length) + 1 + len(length) - 10)
+            return json.loads(response)
+        else:
+            raise MarionetteException("Could not successfully complete transport of message to Gecko, socket closed?")
 
     def connect(self):
         """ Connect to the server and process the hello message we expect