Always close _all_ ijson coroutines, even if doing so raises Exceptions (#14065)

synapse/util/__init__.py

@@ -15,7 +15,7 @@
 import json
 import logging
 import typing
-from typing import Any, Callable, Dict, Generator, Optional
+from typing import Any, Callable, Dict, Generator, Optional, Sequence
 
 import attr
 from frozendict import frozendict
@@ -193,3 +193,15 @@ def log_failure(
 # Version string with git info. Computed here once so that we don't invoke git multiple
 # times.
 SYNAPSE_VERSION = get_distribution_version_string("matrix-synapse", __file__)
+
+
+class ExceptionBundle(Exception):
+    # A poor stand-in for something like Python 3.11's ExceptionGroup.
+    # (A backport called `exceptiongroup` exists but seems overkill: we just want a
+    # container type here.)
+    def __init__(self, message: str, exceptions: Sequence[Exception]):
+        parts = [message]
+        for e in exceptions:
+            parts.append(str(e))
+        super().__init__("\n  - ".join(parts))
+        self.exceptions = exceptions