Update for tornado 6.4

jupyter_server/serverapp.py

@@ -3,6 +3,7 @@
 # Distributed under the terms of the Modified BSD License.
 from __future__ import annotations
 
+import asyncio
 import datetime
 import errno
 import gettext
@@ -2290,7 +2291,11 @@ def _confirm_exit(self) -> None:
         # set it back to original SIGINT handler
         # use IOLoop.add_callback because signal.signal must be called
         # from main thread
-        self.io_loop.add_callback_from_signal(self._restore_sigint_handler)
+        try:
+            loop = asyncio.get_event_loop()
+        except RuntimeError:
+            pass
+        loop.add_signal_handler(self._restore_sigint_handler)
 
     def _signal_stop(self, sig: t.Any, frame: t.Any) -> None:
         """Handle a stop signal."""
@@ -2984,7 +2989,11 @@ def stop(self, from_signal: bool = False) -> None:
             # use IOLoop.add_callback because signal.signal must be called
             # from main thread
             if from_signal:
-                self.io_loop.add_callback_from_signal(self._stop)
+                try:
+                    loop = asyncio.get_event_loop()
+                except RuntimeError:
+                    pass
+                loop.add_signal_handler(self._stop)
             else:
                 self.io_loop.add_callback(self._stop)