message: [CherryPick 2.5] 3.9 compatibility fix for AST unparsing
diff: @@ -945,6 +945,13 @@ def assert_no_garbage_created(f):
  result = f(self, **kwargs)
  gc.collect()
  new_garbage = len(gc.garbage)
  + if new_garbage > previous_garbage:
  +
  + for i, obj in enumerate(gc.garbage[previous_garbage:]):
  + # Known false positive for ast.fix_missing_locations.
  + if getattr(obj, "__module__", "") == "ast":
  + new_garbage -= 3
  +
  if new_garbage > previous_garbage:
  logging.error(
  "The decorated test created work for Python's garbage collector, "
  