fixup! xfail one more test

Author: kernc

pandas/tests/reshape/test_reshape.py

@@ -643,7 +643,7 @@ def test_dataframe_dummies_preserve_categorical_dtype(self):
 class TestGetDummiesSparse(TestGetDummies):
     sparse = True
 
-    @pytest.mark.xfail(reason='nan in index is problematic')
+    @pytest.mark.xfail(reason='nan in index is problematic (GH 16894)')
     def test_include_na(self):
         super(TestGetDummiesSparse, self).test_include_na()
 

pandas/tests/sparse/test_frame.py

@@ -1095,7 +1095,8 @@ def test_as_blocks(self):
         assert list(df_blocks.keys()) == ['float64']
         tm.assert_frame_equal(df_blocks['float64'], df)
 
-    @pytest.mark.xfail(reason='nan column names in _init_dict problematic')
+    @pytest.mark.xfail(reason='nan column names in _init_dict problematic '
+                              '(GH 16894)')
     def test_nan_columnname(self):
         # GH 8822
         nan_colname = DataFrame(Series(1.0, index=[0]), columns=[nan])