bpo-31370: Remove support for threads-less builds (#3385)

* Remove Setup.config
* Always define WITH_THREAD for compatibility.

diff --git a/Lib/logging/config.py b/Lib/logging/config.py
index b3f4e28..c16a75a 100644
--- a/Lib/logging/config.py
+++ b/Lib/logging/config.py
@@ -31,14 +31,9 @@
 import re
 import struct
 import sys
+import threading
 import traceback
 
-try:
-    import _thread as thread
-    import threading
-except ImportError: #pragma: no cover
-    thread = None
-
 from socketserver import ThreadingTCPServer, StreamRequestHandler
 
 
@@ -816,8 +811,6 @@
     normal. Note that you can return transformed bytes, e.g. by decrypting
     the bytes passed in.
     """
-    if not thread: #pragma: no cover
-        raise NotImplementedError("listen() needs threading to work")
 
     class ConfigStreamHandler(StreamRequestHandler):
         """