Raise KeyboardInterrupt when handling SIGINT by default

ipykernel/kernelapp.py

@@ -543,7 +543,7 @@ def register(signum, file=sys.__stderr__, all_threads=True, chain=False, **kwarg
     def sigint_handler(self, *args):
         if self.kernel.shell_is_awaiting:
             self.kernel.shell_interrupt.put(True)
-        elif self.kernel.shell_is_blocking:
+        else:
             raise KeyboardInterrupt
 
     def init_signal(self):