Restore compatibility with Python < 3.9.

Fix #951.

Author: aaugustin

docs/changelog.rst

@@ -30,6 +30,13 @@ They may change at any time.
 
 *In development*
 
+9.0.2
+.....
+
+*In development*
+
+* Restored compatibility of ``python -m websockets`` with Python < 3.9.
+
 9.0.1
 .....
 

src/websockets/__main__.py

@@ -178,11 +178,11 @@ def main() -> None:
 
     # Due to zealous removal of the loop parameter in the Queue constructor,
     # we need a factory coroutine to run in the freshly created event loop.
-    async def queue_factory() -> asyncio.Queue[str]:
+    async def queue_factory() -> "asyncio.Queue[str]":
         return asyncio.Queue()
 
     # Create a queue of user inputs. There's no need to limit its size.
-    inputs: asyncio.Queue[str] = loop.run_until_complete(queue_factory())
+    inputs: "asyncio.Queue[str]" = loop.run_until_complete(queue_factory())
 
     # Create a stop condition when receiving SIGINT or SIGTERM.
     stop: asyncio.Future[None] = loop.create_future()