Change loop exit QTimer to precise

The default QTimer is coarse, so can fire within +-5% of the time specified.
We _need_ to fire after the delay specified so that we exit _after_ schedule_stop_aborting is scheduled.
The QTimer thus needs to be a PreciseTimer.
For small values of stop_on_error_timeout I found the QTimer _still_ fired up to 5ms too early, so added 10ms of delay offset.
singleShot signature is inconsistent between PySide and PyQt, so we store a timer object, similar to ipython#990

ipykernel/eventloops.py

@@ -109,7 +109,16 @@ def process_stream_events():
     # be set from the kernel level
     def _schedule_exit(delay):
         """schedule fall back to main loop in [delay] seconds"""
-        QtCore.QTimer.singleShot(int(1000 * delay), exit_loop)
+        # The signatures of QtCore.QTimer.singleShot are inconsistent between PySide and PyQt
+        # if setting the TimerType, so we create a timer explicitly and store it
+        # to avoid a memory leak.
+        # PreciseTimer is needed so we exit after _at least_ the specified delay, not within 5% of it
+        if not hasattr(kernel, "_qt_timer"):
+            kernel._qt_timer = QtCore.QTimer(kernel.app)
+            kernel._qt_timer.setSingleShot(True)
+            kernel._qt_timer.setTimerType(enum_helper("QtCore.Qt.TimerType").PreciseTimer)
+            kernel._qt_timer.timeout.connect(exit_loop)
+        kernel._qt_timer.start(int(1000 * delay))
 
     loop_qt._schedule_exit = _schedule_exit
 

ipykernel/kernelbase.py

@@ -1211,7 +1211,7 @@ async def stop_aborting():
             # after stop_on_error_timeout, returning to the main io_loop and letting
             # the call_later fire.
             if self.eventloop is not None and hasattr(self.eventloop, "_schedule_exit"):
-                self.eventloop._schedule_exit(self.stop_on_error_timeout)
+                self.eventloop._schedule_exit(self.stop_on_error_timeout + 0.01)
         else:
             schedule_stop_aborting()