asyncio: fix SendfileNotAvailableError availability (#3631)

Author: hauntsaninja

stdlib/3/asyncio/__init__.pyi

@@ -125,9 +125,10 @@ if sys.version_info >= (3, 8):
         TimeoutError as TimeoutError,
     )
 else:
-    from asyncio.events import (
-        SendfileNotAvailableError as SendfileNotAvailableError
-    )
+    if sys.version_info >= (3, 7):
+        from asyncio.events import (
+            SendfileNotAvailableError as SendfileNotAvailableError
+        )
     from asyncio.futures import (
         CancelledError as CancelledError,
         TimeoutError as TimeoutError,

stdlib/3/asyncio/events.pyi

@@ -335,6 +335,5 @@ def _get_running_loop() -> AbstractEventLoop: ...
 
 if sys.version_info >= (3, 7):
     def get_running_loop() -> AbstractEventLoop: ...
-
-if sys.version_info < (3, 8):
-    class SendfileNotAvailableError(RuntimeError): ...
+    if sys.version_info < (3, 8):
+        class SendfileNotAvailableError(RuntimeError): ...