Issue #13532: Check that arguments to sys.stdout.write are strings.

Lib/idlelib/NEWS.txt

 What's New in IDLE 3.2.4?
 =========================
 
+- Issue #13532: Check that arguments to sys.stdout.write are strings.
+
 - Issue # 12510: Attempt to get certain tool tips no longer crashes IDLE.
   Erroneous tool tips have been corrected. Default added for callables.
 

Lib/idlelib/PyShell.py

@@ -1242,6 +1242,8 @@ class PseudoFile(object):
         self.encoding = encoding
 
     def write(self, s):
+        if not isinstance(s, str):
+            raise TypeError('must be str, not ' + type(s).__name__)
         self.shell.write(s, self.tags)
 
     def writelines(self, lines):

Lib/idlelib/run.py

 import sys
+import io
 import linecache
 import time
 import socket
@@ -244,6 +245,23 @@ class MyRPCServer(rpc.RPCServer):
             quitting = True
             thread.interrupt_main()
 
+class _RPCFile(io.TextIOBase):
+    """Wrapper class for the RPC proxy to typecheck arguments 
+    that may not support pickling."""
+
+    def __init__(self, rpc):
+        super.__setattr__(self, 'rpc', rpc)
+
+    def __getattr__(self, name):
+        return getattr(self.rpc, name)
+
+    def __setattr__(self, name, value):
+        return setattr(self.rpc, name, value)
+
+    def write(self, s):
+        if not isinstance(s, str):
+            raise TypeError('must be str, not ' + type(s).__name__)
+        return self.rpc.write(s)
 
 class MyHandler(rpc.RPCHandler):
 
@@ -251,9 +269,9 @@ class MyHandler(rpc.RPCHandler):
         """Override base method"""
         executive = Executive(self)
         self.register("exec", executive)
-        sys.stdin = self.console = self.get_remote_proxy("stdin")
-        sys.stdout = self.get_remote_proxy("stdout")
-        sys.stderr = self.get_remote_proxy("stderr")
+        sys.stdin = self.console = _RPCFile(self.get_remote_proxy("stdin"))
+        sys.stdout = _RPCFile(self.get_remote_proxy("stdout"))
+        sys.stderr = _RPCFile(self.get_remote_proxy("stderr"))
         # page help() text to shell.
         import pydoc # import must be done here to capture i/o binding
         pydoc.pager = pydoc.plainpager