gh-71136: Fix IDLE Shell hang after KeyboardInterrupt under the debugger (#157566)

Debugging 'raise KeyboardInterrupt' in debugged code no longer hangs IDLE forever.  The response is similar to without the debugger.

---------
Co-authored-by: Louie Lu <git@louie.lu>
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

Lib/idlelib/run.py

@@ -164,6 +164,7 @@ def main(del_exitfunc=False):
                     ).start()
 
     while True:
+        request = None
         try:
             if exit_now:
                 try:
@@ -174,9 +175,9 @@ def main(del_exitfunc=False):
             try:
                 request = rpc.request_queue.get(block=True, timeout=0.05)
             except queue.Empty:
-                request = None
                 # Issue 32207: calling handle_tk_events here adds spurious
                 # queue.Empty traceback to event handling exceptions.
+                pass
             if request:
                 seq, (method, args, kwargs) = request
                 ret = method(*args, **kwargs)
@@ -186,6 +187,10 @@ def main(del_exitfunc=False):
         except KeyboardInterrupt:
             if quitting:
                 exit_now = True
+            elif request:
+                # Interrupted while executing a request, as when debugging.
+                print_exception()
+                rpc.response_queue.put((seq, None))
             continue
         except SystemExit:
             capture_warnings(False)

Misc/NEWS.d/next/IDLE/2026-09-15-15-46-35.gh-issue-71136.vwGO0v.rst

@@ -0,0 +1,2 @@
+Fix a hang of the IDLE Shell when code run under the debugger raises
+:exc:`KeyboardInterrupt`.