python3Packages.mcp: skip flaky test on darwin

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

@@ -1,5 +1,6 @@
 {
   lib,
+  stdenv,
   buildPythonPackage,
   fetchFromGitHub,
 
@@ -100,7 +101,8 @@ buildPythonPackage rec {
     "ignore::pydantic.warnings.PydanticDeprecatedSince211"
   ];
 
-  disabledTests = [
+  disabledTests =
+    [
       # attempts to run the package manager uv
       "test_command_execution"
 
@@ -115,6 +117,10 @@ buildPythonPackage rec {
 
       # inline_snapshot._exceptions.UsageError: snapshot value should not change. Use Is(...) for dynamic snapshot parts
       "test_build_metadata"
+    ]
+    ++ lib.optionals stdenv.hostPlatform.isDarwin [
+      # Flaky: ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
+      "test_notification_validation_error"
     ];
 
   __darwinAllowLocalNetworking = true;