https://github.com/lericson/pylibmc/commit/d18ad2911676b4d6b03877ffe94178ea983dc387

From d18ad2911676b4d6b03877ffe94178ea983dc387 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Miro=20Hron=C4=8Dok?= <miro@hroncok.cz>
Date: Wed, 3 Jul 2024 12:58:59 +0200
Subject: [PATCH] Stop accessing None as a dictionary

PyMapping_HasKeyString does not work on None
Accidentally, it used to return false result on silent errors.

Since Python 3.13, this is what happens instead:

    >>> import pylibmc
    >>> m = pylibmc.Client(["10.0.0.1"], binary=True)
    Exception ignored in PyMapping_HasKeyString(); consider using PyMapping_HasKeyStringWithError(), PyMapping_GetOptionalItemString() or PyMapping_GetItemString():
    Traceback (most recent call last):
      File "/usr/lib64/python3.13/site-packages/pylibmc/client.py", line 142, in __init__
        super().__init__(servers=translate_server_specs(servers),
    TypeError: 'NoneType' object is not subscriptable
    ...
    Exception ignored in PyMapping_HasKeyString(); consider using PyMapping_HasKeyStringWithError(), PyMapping_GetOptionalItemString() or PyMapping_GetItemString():
    Traceback (most recent call last):
      File "/usr/lib64/python3.13/site-packages/pylibmc/client.py", line 142, in __init__
        super().__init__(servers=translate_server_specs(servers),
    TypeError: 'NoneType' object is not subscriptable

When this is run via pytest, it leads to:

    pytest.PytestUnraisableExceptionWarning: Exception ignored in PyMapping_HasKeyString(); consider using PyMapping_HasKeyStringWithError(), PyMapping_GetOptionalItemString() or PyMapping_GetItemString(): None

Fixes https://github.com/pallets-eco/cachelib/issues/400
---
 src/_pylibmcmodule.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/_pylibmcmodule.c b/src/_pylibmcmodule.c
index a34d2b5..545b658 100644
--- a/src/_pylibmcmodule.c
+++ b/src/_pylibmcmodule.c
@@ -2082,7 +2082,7 @@ static PyObject *PylibMC_Client_set_behaviors(PylibMC_Client *self,
     char *key;
 
     for (b = PylibMC_behaviors; b->name != NULL; b++) {
-        if (!PyMapping_HasKeyString(behaviors, b->name)) {
+        if (behaviors == Py_None || !PyMapping_HasKeyString(behaviors, b->name)) {
             continue;
         } else if ((py_v = PyMapping_GetItemString(behaviors, b->name)) == NULL) {
             goto error;
@@ -2112,7 +2112,7 @@ static PyObject *PylibMC_Client_set_behaviors(PylibMC_Client *self,
     }
 
     for (b = PylibMC_callbacks; b->name != NULL; b++) {
-        if (!PyMapping_HasKeyString(behaviors, b->name)) {
+        if (behaviors == Py_None || !PyMapping_HasKeyString(behaviors, b->name)) {
             continue;
         } else if ((py_v = PyMapping_GetItemString(behaviors, b->name)) == NULL) {
             goto error;