document invalid enum __init__ behavior

Summary: Somehow we don't have any tests for py3 or python enum `raises ValueError` on invalid int arg to `__init__`

Reviewed By: yoney

Differential Revision: D65001970

fbshipit-source-id: e5a26e995eb56a801d9e1d37fa79d3e80adf27ac

thrift/lib/py3/test/auto_migrate/enums.py

@@ -50,6 +50,7 @@ def test_normal_enum(self) -> None:
         self.assertNotEqual(x.type, Kind.SOCK)
         self.assertIn(x.type, Kind)
         self.assertEqual(int(x.type), 4)
+        self.assertRaises(ValueError, lambda: Kind(47))
 
     def test_normal_enum_not_int(self) -> None:
         x = File(name="/etc", type=Kind.DIR)

thrift/lib/python/test/enums.py

@@ -109,6 +109,7 @@ def test_normal_enum(self) -> None:
         self.assertIsInstance(self.Kind.DIR, int, "Enums are Ints")
         self.assertIn(x.type, self.Kind)
         self.assertEqual(x.type.value, 4)
+        self.assertRaises(ValueError, lambda: self.Kind(47))
 
     def test_enum_value_rename(self) -> None:
         """The value name is None but we auto rename it to None_"""