python311Packages.omegaconf: add attrs to check deps

ImportError while loading conftest '/build/source/tests/conftest.py'.
tests/__init__.py:6: in <module>
    import attr
E   ModuleNotFoundError: No module named 'attr'

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

@@ -1,6 +1,7 @@
 { lib
 , antlr4
 , antlr4-python3-runtime
+, attrs
 , buildPythonPackage
 , fetchFromGitHub
 , setuptools
@@ -55,6 +56,7 @@ buildPythonPackage rec {
   ];
 
   nativeCheckInputs = [
+    attrs
     pydevd
     pytest-mock
     pytestCheckHook