Restore nest-asyncio for tk loop

ipykernel/eventloops.py

@@ -9,7 +9,6 @@
 from functools import partial
 
 import zmq
-from jupyter_core.utils import run_sync
 from packaging.version import Version as V  # noqa
 from traitlets.config.application import Application
 
@@ -251,6 +250,12 @@ def process_stream_events(stream, *a, **kw):
         app.mainloop()
 
     else:
+        import asyncio
+
+        import nest_asyncio
+
+        nest_asyncio.apply()
+
         doi = kernel.do_one_iteration
         # Tk uses milliseconds
         poll_interval = int(1000 * kernel._poll_interval)
@@ -262,8 +267,9 @@ def __init__(self, app, func):
                 self.func = func
 
             def on_timer(self):
+                loop = asyncio.get_event_loop()
                 try:
-                    run_sync(self.func)()
+                    loop.run_until_complete(self.func())
                 except Exception:
                     kernel.log.exception("Error in message handler")
                 self.app.after(poll_interval, self.on_timer)

pyproject.toml

@@ -31,6 +31,8 @@ dependencies = [
     "traitlets>=5.4.0",
     "jupyter_client>=6.1.12",
     "jupyter_core>=4.12,!=5.0.*",
+    # For tk event loop support only.
+    "nest_asyncio",
     "tornado>=6.1",
     "matplotlib-inline>=0.1",
     'appnope;platform_system=="Darwin"',