Message.WhichOneof returns Text, not bytes (#2274)

Author: gvanrossum

third_party/2and3/google/protobuf/message.pyi

@@ -23,7 +23,7 @@ class Message:
     def ListFields(self) -> Sequence[Tuple[FieldDescriptor, Any]]: ...
     def HasField(self, field_name: Text) -> bool: ...
     def ClearField(self, field_name: Text) -> None: ...
-    def WhichOneof(self, oneof_group) -> Optional[bytes]: ...
+    def WhichOneof(self, oneof_group) -> Optional[Text]: ...
     def HasExtension(self, extension_handle): ...
     def ClearExtension(self, extension_handle): ...
     def ByteSize(self) -> int: ...