Allow nested tuples in isinstance/issubclass (#998)

Fixes #997

Author: pkch

stdlib/2/__builtin__.pyi

@@ -718,8 +718,8 @@ def intern(string: str) -> str: ...
 def iter(iterable: Iterable[_T]) -> Iterator[_T]: ...
 @overload
 def iter(function: Callable[[], _T], sentinel: _T) -> Iterator[_T]: ...
-def isinstance(o: object, t: Union[type, Tuple[type, ...]]) -> bool: ...
-def issubclass(cls: type, classinfo: Union[type, Tuple[type, ...]]) -> bool: ...
+def isinstance(o: object, t: Union[type, Tuple[Union[type, Tuple], ...]]) -> bool: ...
+def issubclass(cls: type, classinfo: Union[type, Tuple[Union[type, Tuple], ...]]) -> bool: ...
 def len(o: Sized) -> int: ...
 @overload
 def map(func: Callable[[_T1], _S], iter1: Iterable[_T1]) -> List[_S]: ...

stdlib/3/builtins.pyi

@@ -773,8 +773,8 @@ def input(prompt: Any = None) -> str: ...
 def iter(iterable: Iterable[_T]) -> Iterator[_T]: ...
 @overload
 def iter(function: Callable[[], _T], sentinel: _T) -> Iterator[_T]: ...
-def isinstance(o: object, t: Union[type, Tuple[type, ...]]) -> bool: ...
-def issubclass(cls: type, classinfo: Union[type, Tuple[type, ...]]) -> bool: ...
+def isinstance(o: object, t: Union[type, Tuple[Union[type, Tuple], ...]]) -> bool: ...
+def issubclass(cls: type, classinfo: Union[type, Tuple[Union[type, Tuple], ...]]) -> bool: ...
 def len(o: Sized) -> int: ...
 def license() -> None: ...
 def locals() -> Dict[str, Any]: ...