make extra_arguments configurable

tdpetrou · tdpetrou · commit 0deb5b2af465 · 2020-05-21T10:00:04.000-04:00
diff --git a/nbclient/client.py b/nbclient/client.py
@@ -133,7 +133,7 @@ class NotebookClient(LoggingConfigurable):
         ),
     ).tag(config=True)
 
-    extra_arguments = List(Unicode())
+    extra_arguments = List(Unicode()).tag(config=True)
 
     kernel_name = Unicode(
         '',
