python3Packages.python-lsp-black: fix build

Two independent breakages on the default Python 3.14 / setuptools 82 stack:

- tests/test_plugin.py imports pkg_resources, which setuptools 81+ no longer
  ships; add setuptools_80 to nativeCheckInputs so it is available at test time.
- black 26.5 split SourceASTParseError out of ASTSafetyError, which the plugin
  did not catch; backport the upstream fix (python-lsp-black#65).

Assisted-by: Claude Code (Claude Opus 4.8)

pkgs/development/python-modules/python-lsp-black/default.nix

@@ -15,6 +15,7 @@
 
   # checks
   pytestCheckHook,
+  setuptools_80,
 }:
 
 buildPythonPackage rec {
@@ -41,7 +42,14 @@ buildPythonPackage rec {
     ++ lib.optional (lib.versionAtLeast black.version "24.3.0") (fetchpatch {
       url = "https://github.com/python-lsp/python-lsp-black/commit/9298585a9d14d25920c33b188d79e820dc98d4a9.patch";
       hash = "sha256-4u0VIS7eidVEiKRW2wc8lJVkJwhzJD/M+uuqmTtiZ7E=";
-    });
+    })
+    # https://github.com/python-lsp/python-lsp-black/pull/65 (black >= 26.5)
+    ++ [
+      (fetchpatch {
+        url = "https://github.com/python-lsp/python-lsp-black/commit/35b5bc6f944bddac0c896127dc44a9404e95f482.patch";
+        hash = "sha256-FRxM8leFVkPjRiR3wNjy5g5BazHc6ZvtnoI8Qgz4co4=";
+      })
+    ];
 
   build-system = [ setuptools ];
 
@@ -52,7 +60,10 @@ buildPythonPackage rec {
 
   pythonImportsCheck = [ "pylsp_black" ];
 
-  nativeCheckInputs = [ pytestCheckHook ];
+  nativeCheckInputs = [
+    pytestCheckHook
+    setuptools_80 # for pkg_resources, removed in setuptools 81+ (tests/test_plugin.py)
+  ];
 
   meta = {
     homepage = "https://github.com/python-lsp/python-lsp-black";