Fix 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 contributed by Karl.

Lib/http/server.py

@@ -426,7 +426,7 @@ class BaseHTTPRequestHandler(socketserver.StreamRequestHandler):
         content = (self.error_message_format %
                    {'code': code, 'message': _quote_html(message), 'explain': explain})
         body = content.encode('UTF-8', 'replace')
-        self.send_response(code, message)
+        self.send_response(code, shortmsg)
         self.send_header("Content-Type", self.error_content_type)
         self.send_header('Connection', 'close')
         self.send_header('Content-Length', int(len(body)))

Misc/NEWS

@@ -275,6 +275,10 @@ 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.