asyncio: fix various version availability (#3638)

stdlib/3/asyncio/futures.pyi

@@ -17,13 +17,14 @@ if sys.version_info >= (3, 7):
 _T = TypeVar('_T')
 _S = TypeVar('_S')
 
-class _TracebackLogger:
-    exc: BaseException
-    tb: List[str]
-    def __init__(self, exc: Any, loop: AbstractEventLoop) -> None: ...
-    def activate(self) -> None: ...
-    def clear(self) -> None: ...
-    def __del__(self) -> None: ...
+if sys.version_info < (3, 7):
+    class _TracebackLogger:
+        exc: BaseException
+        tb: List[str]
+        def __init__(self, exc: Any, loop: AbstractEventLoop) -> None: ...
+        def activate(self) -> None: ...
+        def clear(self) -> None: ...
+        def __del__(self) -> None: ...
 
 def isfuture(obj: object) -> bool: ...
 
@@ -32,7 +33,8 @@ class Future(Awaitable[_T], Iterable[_T]):
     _exception: BaseException
     _blocking = False
     _log_traceback = False
-    _tb_logger: Type[_TracebackLogger]
+    if sys.version_info < (3, 6):
+        _tb_logger: Type[_TracebackLogger]
     def __init__(self, *, loop: Optional[AbstractEventLoop] = ...) -> None: ...
     def __repr__(self) -> str: ...
     def __del__(self) -> None: ...

stdlib/3/asyncio/tasks.pyi

@@ -115,7 +115,8 @@ class Task(Future[_T], Generic[_T]):
     def print_stack(self, *, limit: int = ..., file: TextIO = ...) -> None: ...
     def cancel(self) -> bool: ...
     def _step(self, value: Any = ..., exc: Exception = ...) -> None: ...
-    def _wakeup(self, future: Future[Any]) -> None: ...
+    if sys.version_info < (3, 7):
+        def _wakeup(self, future: Future[Any]) -> None: ...
 
 if sys.version_info >= (3, 7):
     def all_tasks(loop: Optional[AbstractEventLoop] = ...) -> Set[Task[Any]]: ...