python314Packages.dask: fix tests

Without this patch, a lot of them fail with error messages like

    _pickle.PicklingError: Can't pickle local object <function test_column_projection_map_partitions.<locals>.myfunc at 0x7fff7517b8a0

and one test fails with

    dask.multiprocessing.TypeError: cannot pickle 'itertools.chain' object

pkgs/development/python-modules/dask/default.nix

@@ -2,6 +2,7 @@
   lib,
   buildPythonPackage,
   fetchFromGitHub,
+  pythonAtLeast,
 
   # build-system
   setuptools,
@@ -49,6 +50,12 @@ buildPythonPackage rec {
     hash = "sha256-cU4w4dqJQ3ew+fRyD7Lc4URNfW738kKqls6k6j65pIo=";
   };
 
+  # https://github.com/dask/dask/issues/12043
+  postPatch = lib.optionalString (pythonAtLeast "3.14") ''
+    substituteInPlace dask/dataframe/dask_expr/tests/_util.py \
+      --replace-fail "except AttributeError:" "except (AttributeError, pickle.PicklingError):"
+  '';
+
   build-system = [
     setuptools
     setuptools-scm
@@ -112,6 +119,11 @@ buildPythonPackage rec {
     "network"
   ];
 
+  # https://github.com/dask/dask/issues/12042
+  disabledTests = lib.optionals (pythonAtLeast "3.14") [
+    "test_multiple_repartition_partition_size"
+  ];
+
   __darwinAllowLocalNetworking = true;
 
   pythonImportsCheck = [