Issue12541 - Add UserWarning for unquoted realms

Lib/test/test_urllib2.py

@@ -1227,6 +1227,7 @@ class HandlerTests(unittest.TestCase):
             401, 'WWW-Authenticate: Basic realm=%s\r\n\r\n' % realm)
         opener.add_handler(auth_handler)
         opener.add_handler(http_handler)
+        with self.assertWarns(UserWarning):
             self._test_basic_auth(opener, auth_handler, "Authorization",
                                 realm, http_handler, password_manager,
                                 "http://acme.example.com/protected",

Lib/urllib/request.py

@@ -95,6 +95,7 @@ import socket
 import sys
 import time
 import collections
+import warnings
 
 from urllib.error import URLError, HTTPError, ContentTooShortError
 from urllib.parse import (
@@ -827,6 +828,9 @@ class AbstractBasicAuthHandler:
             mo = AbstractBasicAuthHandler.rx.search(authreq)
             if mo:
                 scheme, quote, realm = mo.groups()
+                if quote not in ["'", '"']:
+                    warnings.warn("Basic Auth Realm was unquoted",
+                                  UserWarning, 2)
                 if scheme.lower() == 'basic':
                     response = self.retry_http_basic_auth(host, req, realm)
                     if response and response.code != 401: