Take asynccontextmanager from contextlib now that we dropped Python 3.6.

Author: jonathanslenders

src/prompt_toolkit/application/run_in_terminal.py

@@ -3,18 +3,13 @@
 """
 import sys
 from asyncio import Future, ensure_future
+from contextlib import asynccontextmanager
 from typing import AsyncGenerator, Awaitable, Callable, TypeVar
 
 from prompt_toolkit.eventloop import run_in_executor_with_context
 
 from .current import get_app_or_none
 
-if sys.version_info >= (3, 7):
-    from contextlib import asynccontextmanager
-else:
-    from prompt_toolkit.eventloop.async_context_manager import asynccontextmanager
-
-
 __all__ = [
     "run_in_terminal",
     "in_terminal",

src/prompt_toolkit/eventloop/async_context_manager.py

@@ -2,10 +2,10 @@
 Implementation for async generators.
 """
 from asyncio import get_running_loop
+from contextlib import asynccontextmanager
 from queue import Empty, Full, Queue
 from typing import Any, AsyncGenerator, Callable, Iterable, TypeVar, Union
 
-from .async_context_manager import asynccontextmanager
 from .utils import run_in_executor_with_context
 
 __all__ = [