Reverting the changeset 5126e62c60af made for Issue #12921

Lib/http/server.py

@@ -421,7 +421,7 @@ class BaseHTTPRequestHandler(socketserver.StreamRequestHandler):
         # using _quote_html to prevent Cross Site Scripting attacks (see bug #1100201)
         content = (self.error_message_format %
                    {'code': code, 'message': _quote_html(message), 'explain': explain})
-        self.send_response(code, shortmsg)
+        self.send_response(code, message)
         self.send_header("Content-Type", self.error_content_type)
         self.send_header('Connection', 'close')
         self.end_headers()

Misc/NEWS

@@ -233,10 +233,6 @@ Core and Builtins
 Library
 -------
 
-- Issue #12921: BaseHTTPServer's send_error should send the correct error
-  response message when  send_error includes a message in addition to error
-  status. Patch submitted by Karl.
-
 - Issue #17278: Fix a crash in heapq.heappush() and heapq.heappop() when
   the list is being resized concurrently.