From 75a1cbdd38b142b359849eae16a2ecc12f6b3881 Mon Sep 17 00:00:00 2001
From: Petr Viktorin <encukou@gmail.com>
Date: Thu, 30 Oct 2025 12:14:17 +0100
Subject: [PATCH] gh-140748: socket_helper.transient_internet: Unwrap
 UrlError.__cause__ (GH-140749)

---
 Lib/test/support/socket_helper.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Lib/test/support/socket_helper.py b/Lib/test/support/socket_helper.py
index 87941ee1791b..a41e487f3e4b 100644
--- a/Lib/test/support/socket_helper.py
+++ b/Lib/test/support/socket_helper.py
@@ -259,6 +259,10 @@ def transient_internet(resource_name, *, timeout=_NOT_SET, errnos=()):
             #        raise OSError('socket error', msg) from msg
             elif len(a) >= 2 and isinstance(a[1], OSError):
                 err = a[1]
+            # The error can also be wrapped as __cause__:
+            #    raise URLError(f"ftp error: {exp}") from exp
+            elif isinstance(err, urllib.error.URLError) and err.__cause__:
+                err = err.__cause__
             else:
                 break
         filter_error(err)
-- 
2.47.3