From 9210eff61b75edabbe9263df0c4a303fc2149a22 Mon Sep 17 00:00:00 2001
From: "Miss Islington (bot)"
 <31488909+miss-islington@users.noreply.github.com>
Date: Wed, 13 Oct 2021 11:00:05 -0700
Subject: [PATCH] bpo-45386: Handle strftime's ValueError graciously in
 xmlrpc.client (GH-28765) (GH-28935)

At import time, the xmlrpc.client module uses different date formats to
test strftime so it can format years with 4 digits consistently.
Depending on the underlying C library and its strftime implementation
some of these calls can result in ValueErrors, blocking the
xmlrpc.client module from being imported.

This commit changes the behavior of this bit of code to react to
ValueError exceptions, treating the format that caused them as an
non-viable option.
(cherry picked from commit 1c831353816ff699b54e804047a7242a09e98f5b)

Co-authored-by: rtobar <rtobarc@gmail.com>
---
 Lib/xmlrpc/client.py                                   | 10 ++++++++--
 .../Library/2021-10-07-00-05-05.bpo-45386.q9ORpA.rst   |  3 +++
 2 files changed, 11 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2021-10-07-00-05-05.bpo-45386.q9ORpA.rst

diff --git a/Lib/xmlrpc/client.py b/Lib/xmlrpc/client.py
index 9e7449c88dfc0d..a614cef6ab2f1a 100644
--- a/Lib/xmlrpc/client.py
+++ b/Lib/xmlrpc/client.py
@@ -264,16 +264,22 @@ def __repr__(self):
 
 # Issue #13305: different format codes across platforms
 _day0 = datetime(1, 1, 1)
-if _day0.strftime('%Y') == '0001':      # Mac OS X
+def _try(fmt):
+    try:
+        return _day0.strftime(fmt) == '0001'
+    except ValueError:
+        return False
+if _try('%Y'):      # Mac OS X
     def _iso8601_format(value):
         return value.strftime("%Y%m%dT%H:%M:%S")
-elif _day0.strftime('%4Y') == '0001':   # Linux
+elif _try('%4Y'):   # Linux
     def _iso8601_format(value):
         return value.strftime("%4Y%m%dT%H:%M:%S")
 else:
     def _iso8601_format(value):
         return value.strftime("%Y%m%dT%H:%M:%S").zfill(17)
 del _day0
+del _try
 
 
 def _strftime(value):
diff --git a/Misc/NEWS.d/next/Library/2021-10-07-00-05-05.bpo-45386.q9ORpA.rst b/Misc/NEWS.d/next/Library/2021-10-07-00-05-05.bpo-45386.q9ORpA.rst
new file mode 100644
index 00000000000000..eec77ceccf9338
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-10-07-00-05-05.bpo-45386.q9ORpA.rst
@@ -0,0 +1,3 @@
+Make :mod:`xmlrpc.client` more robust to C runtimes where the underlying C
+``strftime`` function results in a ``ValueError`` when testing for year
+formatting options.