TST: add failing case for mixed

Author: TomAugspurger

pandas/tests/dtypes/test_dtypes.py

@@ -618,3 +618,8 @@ def test_categorical_equality(self, ordered, other, expected):
         c1 = CategoricalDtype(['a', 'b'], ordered)
         result = c1 == other
         assert result == expected
+
+    def test_mixed(self):
+        a = CategoricalDtype(['a', 'b', 1, 2])
+        b = CategoricalDtype(['a', 'b', '1', '2'])
+        assert hash(a) != hash(b)