Fix ijson coroutines test

tests/federation/transport/test_client.py

@@ -15,6 +15,8 @@
 import json
 from unittest.mock import Mock
 
+import ijson.common
+
 from synapse.api.room_versions import RoomVersions
 from synapse.federation.transport.client import SendJoinParser
 from synapse.util import ExceptionBundle
@@ -117,8 +119,17 @@ def test_errors_closing_coroutines(self) -> None:
         coro_3 = Mock()
         coro_3.close = Mock(side_effect=RuntimeError("Couldn't close coro 3"))
 
+        original_coros = parser._coros
         parser._coros = [coro_1, coro_2, coro_3]
 
+        # Close the original coroutines. If we don't, when we garbage collect them
+        # they will throw, failing the test. (Oddly, this only started in CPython 3.11).
+        for coro in original_coros:
+            try:
+                coro.close()
+            except ijson.common.IncompleteJSONError:
+                pass
+
         # Send half of the data to the parser
         parser.write(serialisation[: len(serialisation) // 2])