Missing kernel property

ipykernel/comm/comm.py

@@ -12,6 +12,11 @@
 class Comm(BaseComm):
     """Class for communicating between a Frontend and a Kernel"""
 
+    def __init__(self, *args, **kwargs):
+        super(Comm, self).__init__(*args, **kwargs)
+
+        self.kernel = None
+
     def publish_msg(self, msg_type, data=None, metadata=None, buffers=None, **keys):
         """Helper for sending a comm message on IOPub"""
         if not Kernel.initialized():
@@ -21,14 +26,15 @@ def publish_msg(self, msg_type, data=None, metadata=None, buffers=None, **keys):
         metadata = {} if metadata is None else metadata
         content = json_clean(dict(data=data, comm_id=self.comm_id, **keys))
 
-        kernel = Kernel.instance()
+        if self.kernel is None:
+            self.kernel = Kernel.instance()
 
-        kernel.session.send(
-            kernel.iopub_socket,
+        self.kernel.session.send(
+            self.kernel.iopub_socket,
             msg_type,
             content,
             metadata=json_clean(metadata),
-            parent=kernel.get_parent("shell"),
+            parent=self.kernel.get_parent("shell"),
             ident=self.topic,
             buffers=buffers,
         )