Merge pull request #21903 from lidizheng/aio-fix-close

[Aio] Attempt to fix recent AsyncIO windows flake

src/python/grpcio/grpc/experimental/aio/_channel.py

@@ -44,7 +44,10 @@ class _OngoingCalls:
         self._calls = WeakSet()
 
     def _remove_call(self, call: _base_call.RpcContext):
-        self._calls.remove(call)
+        try:
+            self._calls.remove(call)
+        except KeyError:
+            pass
 
     @property
     def calls(self) -> AbstractSet[_base_call.RpcContext]:

src/python/grpcio_tests/tests_aio/unit/close_channel_test.py

@@ -24,11 +24,11 @@ from grpc.experimental.aio import _base_call
 from grpc.experimental.aio._channel import _OngoingCalls
 
 from src.proto.grpc.testing import messages_pb2, test_pb2_grpc
-from tests_aio.unit._constants import UNARY_CALL_WITH_SLEEP_VALUE
 from tests_aio.unit._test_base import AioTestBase
 from tests_aio.unit._test_server import start_test_server
 
 _UNARY_CALL_METHOD_WITH_SLEEP = '/grpc.testing.TestService/UnaryCallWithSleep'
+_LONG_TIMEOUT_THAT_SHOULD_NOT_EXPIRE = 60
 
 
 class TestOngoingCalls(unittest.TestCase):
@@ -90,7 +90,7 @@ class TestCloseChannel(AioTestBase):
 
         call = UnaryCallWithSleep(messages_pb2.SimpleRequest())
 
-        await channel.close(grace=UNARY_CALL_WITH_SLEEP_VALUE * 4)
+        await channel.close(grace=_LONG_TIMEOUT_THAT_SHOULD_NOT_EXPIRE)
 
         self.assertEqual(grpc.StatusCode.OK, await call.code())