Make PY2 enum more like PY3 enum, fixing bug in unique() (#1668)

third_party/2/enum.pyi

@@ -1,8 +1,20 @@
-from typing import List, Any, TypeVar, Type, Iterable, Iterator
+from typing import List, Any, TypeVar, Union, Iterable, Iterator, TypeVar, Generic, Type, Sized, Reversible, Container, Mapping
+from abc import ABCMeta
 
 _T = TypeVar('_T', bound=Enum)
-class EnumMeta(type, Iterable[Enum]):
-    def __iter__(self: Type[_T]) -> Iterator[_T]: ...  # type: ignore
+_S = TypeVar('_S', bound=Type[Enum])
+
+# Note: EnumMeta actually subclasses type directly, not ABCMeta.
+# This is a temporary workaround to allow multiple creation of enums with builtins
+# such as str as mixins, which due to the handling of ABCs of builtin types, cause
+# spurious inconsistent metaclass structure. See #1595.
+class EnumMeta(ABCMeta, Iterable[Enum], Sized, Reversible[Enum], Container[Enum]):
+    def __iter__(self: Type[_T]) -> Iterator[_T]: ...
+    def __reversed__(self: Type[_T]) -> Iterator[_T]: ...
+    def __contains__(self, member: Any) -> bool: ...
+    def __getitem__(self: Type[_T], name: str) -> _T: ...
+    @property
+    def __members__(self: Type[_T]) -> Mapping[str, _T]: ...
 
 class Enum(metaclass=EnumMeta):
     def __new__(cls: Type[_T], value: Any) -> _T: ...
@@ -18,4 +30,4 @@ class Enum(metaclass=EnumMeta):
 
 class IntEnum(int, Enum): ...
 
-def unique(enumeration: _T) -> _T: ...
+def unique(enumeration: _S) -> _S: ...