add skip if no cuda decorator to pg wrapper test (#649)

Summary:
Pull Request resolved: #649

This test needs a GPU

Reviewed By: JKSenthil

Differential Revision: D51966203

fbshipit-source-id: 9f99711667f9265e72b85cba81159a34e220edd1

tests/utils/test_distributed_gpu.py

@@ -43,6 +43,11 @@ def _test_ddp_gather_uneven_tensors_multidim_nccl() -> None:
             assert val.shape == (idx + 1, 4 - idx)
             assert (val == 1).all()
 
+    @unittest.skipUnless(
+        condition=cuda_available,
+        reason="This test should only run on a GPU host.",
+    )
+    @unittest.skipUnless(dist_available, reason="Torch distributed is needed to run")
     def test_pg_wrapper_scatter_object_list_nccl(self) -> None:
         spawn_multi_process(
             2,