From 1d9563530f9105df34cc5b635cc7965e90c1950c Mon Sep 17 00:00:00 2001
From: Zach Sailer <zsailer@apple.com>
Date: Sat, 30 Apr 2022 17:47:32 -0700
Subject: [PATCH] allow empty event bus

---
 jupyter_server/serverapp.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/jupyter_server/serverapp.py b/jupyter_server/serverapp.py
index 111dbf6a19..a5f9b99d10 100644
--- a/jupyter_server/serverapp.py
+++ b/jupyter_server/serverapp.py
@@ -1571,6 +1571,7 @@ def _default_kernel_spec_manager_class(self):
 
     event_bus = Instance(
         EventBus,
+        allow_none=True,
         help="An EventBus for emitting structured event data from Jupyter Server and extensions.",
     )