xfail another dask/pyarrow test (#8636)

* xfail another dask/pyarrow test

Unsure why this wasn't showing prior -- having tests fail in the good state does make it much more difficult to ensure everything is fixed before merging.

xarray/core/utils.py

@@ -1248,7 +1248,12 @@ def find_stack_level(test_mode=False) -> int:
     pkg_dir = Path(xr.__file__).parent
     test_dir = pkg_dir / "tests"
 
-    std_lib_dir = Path(sys.modules["os"].__file__).parent  # Standard library path
+    std_lib_init = sys.modules["os"].__file__
+    # Mostly to appease mypy; I don't think this can happen...
+    if std_lib_init is None:
+        return 0
+
+    std_lib_dir = Path(std_lib_init).parent
 
     frame = inspect.currentframe()
     n = 0

xarray/tests/test_dask.py

@@ -867,6 +867,10 @@ def test_to_dask_dataframe_coordinates(self):
         assert isinstance(actual, dd.DataFrame)
         assert_frame_equal(expected.compute(), actual.compute())
 
+    @pytest.mark.xfail(
+        reason="Currently pandas with pyarrow installed will return a `string[pyarrow]` type, "
+        "which causes the index to have a different type depending on whether pyarrow is installed"
+    )
     def test_to_dask_dataframe_not_daskarray(self):
         # Test if DataArray is not a dask array
         x = np.random.randn(10)