sys: Correct types of sys.displayhook, sys.excepthook and variants (#3673)

displayhook should accept any object, not just integers.

displayhook and excepthook may be assigned to, so they should be
Callable values rather than function definitions. That way it's fine
to assign a function with different argument names. Their dunder
variants are supposed to be constant.

stdlib/2/sys.pyi

@@ -89,8 +89,8 @@ last_traceback: TracebackType
 meta_path: List[Any]
 path_hooks: List[Any]
 path_importer_cache: Dict[str, Any]
-displayhook: Optional[Callable[[int], None]]
-excepthook: Optional[Callable[[type, BaseException, TracebackType], None]]
+displayhook: Callable[[object], Any]
+excepthook: Callable[[Type[BaseException], BaseException, TracebackType], Any]
 exc_type: Optional[type]
 exc_value: Union[BaseException, ClassType]
 exc_traceback: TracebackType
@@ -112,7 +112,7 @@ def _clear_type_cache() -> None: ...
 def _current_frames() -> Dict[int, FrameType]: ...
 def _getframe(depth: int = ...) -> FrameType: ...
 def call_tracing(fn: Any, args: Any) -> Any: ...
-def __displayhook__(value: int) -> None: ...
+def __displayhook__(value: object) -> None: ...
 def __excepthook__(type_: type, value: BaseException, traceback: TracebackType) -> None: ...
 def exc_clear() -> None: ...
 def exc_info() -> _OptExcInfo: ...

stdlib/3/sys.pyi

@@ -28,8 +28,8 @@ builtin_module_names: Sequence[str]  # actually a tuple of strings
 copyright: str
 # dllhandle = 0  # Windows only
 dont_write_bytecode: bool
-__displayhook__: Any  # contains the original value of displayhook
-__excepthook__: Any  # contains the original value of excepthook
+displayhook: Callable[[object], Any]
+excepthook: Callable[[Type[BaseException], BaseException, TracebackType], Any]
 exec_prefix: str
 executable: str
 float_repr_style: str
@@ -131,9 +131,9 @@ def call_tracing(fn: Callable[..., _T], args: Any) -> _T: ...
 def _clear_type_cache() -> None: ...
 def _current_frames() -> Dict[int, Any]: ...
 def _debugmallocstats() -> None: ...
-def displayhook(value: Optional[int]) -> None: ...
-def excepthook(type_: Type[BaseException], value: BaseException,
-               traceback: TracebackType) -> None: ...
+def __displayhook__(value: object) -> None: ...
+def __excepthook__(type_: Type[BaseException], value: BaseException,
+                   traceback: TracebackType) -> None: ...
 def exc_info() -> _OptExcInfo: ...
 # sys.exit() accepts an optional argument of anything printable
 def exit(arg: object = ...) -> NoReturn: ...