Issue #14200: Idle shell crash on printing non-BMP unicode character.

UnicodeEncodeError is raised for strings contains non-BMP characters.
For eval results unicode escaping is used, print() calls display
exception with traceback as usual.

Lib/idlelib/run.py

@@ -6,6 +6,7 @@ import traceback
 import _thread as thread
 import threading
 import queue
+import builtins
 
 from idlelib import CallTips
 from idlelib import AutoComplete
@@ -261,6 +262,25 @@ class MyRPCServer(rpc.RPCServer):
             thread.interrupt_main()
 
 
+def displayhook(value):
+    """Override standard display hook to use non-locale encoding"""
+    if value is None:
+        return
+    # Set '_' to None to avoid recursion
+    builtins._ = None
+    text = repr(value)
+    try:
+        sys.stdout.write(text)
+    except UnicodeEncodeError:
+        # let's use ascii while utf8-bmp codec doesn't present
+        encoding = 'ascii'
+        bytes = text.encode(encoding, 'backslashreplace')
+        text = bytes.decode(encoding, 'strict')
+        sys.stdout.write(text)
+    sys.stdout.write("\n")
+    builtins._ = value
+
+
 class MyHandler(rpc.RPCHandler):
 
     def handle(self):
@@ -270,6 +290,7 @@ class MyHandler(rpc.RPCHandler):
         sys.stdin = self.console = self.get_remote_proxy("stdin")
         sys.stdout = self.get_remote_proxy("stdout")
         sys.stderr = self.get_remote_proxy("stderr")
+        sys.displayhook = displayhook
         # page help() text to shell.
         import pydoc # import must be done here to capture i/o binding
         pydoc.pager = pydoc.plainpager