[Tests] Add MPS skip decorator (huggingface#2362)

* finish

* Apply suggestions from code review

* fix indent and import error in test_stable_diffusion_depth

---------

Co-authored-by: William Berman <[email protected]>

Author: patrickvonplaten

utils/__init__.py

@@ -79,6 +79,7 @@
         parse_flag_from_env,
         print_tensor_test,
         require_torch_gpu,
+        skip_mps,
         slow,
         torch_all_close,
         torch_device,

utils/testing_utils.py

@@ -163,6 +163,11 @@ def require_torch_gpu(test_case):
     )
 
 
+def skip_mps(test_case):
+    """Decorator marking a test to skip if torch_device is 'mps'"""
+    return unittest.skipUnless(torch_device != "mps", "test requires non 'mps' device")(test_case)
+
+
 def require_flax(test_case):
     """
     Decorator marking a test that requires JAX & Flax. These tests are skipped when one / both are not installed