Try to serialize a set to XCom, get unhelpful error message. #28048

from airflow.models import DAG
from airflow.operators.python import PythonOperator
from datetime import datetime, timedelta

def cant_serialize():
    return {1: {"one", "two"}, 2: {"check", "one", "two"}}

with DAG(
    dag_id="some_sets",
    start_date=datetime(2022, 1, 1),
    schedule_interval=None,
) as dag:

    PythonOperator(
        task_id="some_sets",
        python_callable=cant_serialize,
    )
# Traceback (most recent call last):
#   File "/Users/matt/src/airflow/airflow/utils/session.py", line 72, in wrapper
#     return func(*args, **kwargs)
#   File "/Users/matt/src/airflow/airflow/models/taskinstance.py", line 2294, in xcom_push
#     XCom.set(
#   File "/Users/matt/src/airflow/airflow/utils/session.py", line 72, in wrapper
#     return func(*args, **kwargs)
#   File "/Users/matt/src/airflow/airflow/models/xcom.py", line 234, in set
#     value = cls.serialize_value(
#   File "/Users/matt/src/airflow/airflow/models/xcom.py", line 627, in serialize_value
#     return json.dumps(value, cls=XComEncoder).encode("UTF-8")
#   File "/Users/matt/.pyenv/versions/3.10.6/lib/python3.10/json/__init__.py", line 238, in dumps
#     **kw).encode(obj)
#   File "/Users/matt/src/airflow/airflow/utils/json.py", line 176, in encode
#     return super().encode(o)
#   File "/Users/matt/.pyenv/versions/3.10.6/lib/python3.10/json/encoder.py", line 199, in encode
#     chunks = self.iterencode(o, _one_shot=True)
#   File "/Users/matt/.pyenv/versions/3.10.6/lib/python3.10/json/encoder.py", line 257, in iterencode
#     return _iterencode(o, 0)
#   File "/Users/matt/src/airflow/airflow/utils/json.py", line 153, in default
#     CLASSNAME: o.__module__ + "." + o.__class__.__qualname__,
# AttributeError: 'set' object has no attribute '__module__'. Did you mean: '__reduce__'?