Merge pull request #1001 from Unity-Technologies/hotfix-grpc-multiprocessing

[Hotfix] Made the Pipe of the grpc communicator an instance property

Author: awjuliani

python/unityagents/rpc_communicator.py

@@ -15,7 +15,8 @@
 
 
 class UnityToExternalServicerImplementation(UnityToExternalServicer):
-    parent_conn, child_conn = Pipe()
+    def __init__(self):
+        self.parent_conn, self.child_conn = Pipe()
 
     def Initialize(self, request, context):
         self.child_conn.send(request)