Crash in automatic update handler when submitting work_on_bugs_task

[mattiaverga]

From bodhi-consumer logs:

2020-10-25 11:17:14,460 INFO  [fedora_messaging.twisted.protocol][MainThread] Consuming message from topic org.fedoraproject.prod.buildsys.tag (message id c2d97737-444f-49b4-b4ca-1efb3a05e941)
2020-10-25 11:17:14,463 INFO  [bodhi][PoolThread-twisted.internet.reactor-1] Received message from fedora-messaging with topic: org.fedoraproject.prod.buildsys.tag
2020-10-25 11:17:14,463 INFO  [bodhi][PoolThread-twisted.internet.reactor-1] ginac-1.7.9-5.fc34 tagged into f34-updates-candidate
2020-10-25 11:17:14,469 INFO  [bodhi][PoolThread-twisted.internet.reactor-1] Build was not submitted, skipping
2020-10-25 11:17:14,838 INFO  [bodhi.server][PoolThread-twisted.internet.reactor-1] Sending mail to ---@posteo.de: [Fedora Update] [comment] ginac-1.7.9-5.fc34
2020-10-25 11:17:15,016 ERROR [bodhi][PoolThread-twisted.internet.reactor-1] Instance <Update at 0x7fa3740f5910> is not bound to a Session; attribute refresh operation cannot proceed (Background on this error at: http://sqlalche.me/e/13/bhk3):  Unable to handle message in Automatic Update handler: Id: c2d97737-444f-49b4-b4ca-1efb3a05e941
Topic: org.fedoraproject.prod.buildsys.tag
Headers: {
    "fedora_messaging_schema": "base.message",
    "fedora_messaging_severity": 20,
    "sent-at": "2020-10-25T11:17:14+00:00"
}
Body: {
    "build_id": 1634116,
    "instance": "primary",
    "name": "ginac",
    "owner": "---",
    "release": "5.fc34",
    "tag": "f34-updates-candidate",
    "tag_id": 27040,
    "user": "---",
    "version": "1.7.9"
}
Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/bodhi/server/consumers/__init__.py", line 79, in __call__
    handler_info.handler(msg)
  File "/usr/local/lib/python3.8/site-packages/bodhi/server/consumers/automatic_updates.py", line 197, in __call__
    alias = update.alias
  File "/usr/lib64/python3.8/site-packages/sqlalchemy/orm/attributes.py", line 287, in __get__
    return self.impl.get(instance_state(instance), dict_)
  File "/usr/lib64/python3.8/site-packages/sqlalchemy/orm/attributes.py", line 718, in get
    value = state._load_expired(state, passive)
  File "/usr/lib64/python3.8/site-packages/sqlalchemy/orm/state.py", line 652, in _load_expired
    self.manager.deferred_scalar_loader(self, toload)
  File "/usr/lib64/python3.8/site-packages/sqlalchemy/orm/loading.py", line 944, in load_scalar_attributes
    raise orm_exc.DetachedInstanceError(
sqlalchemy.orm.exc.DetachedInstanceError: Instance <Update at 0x7fa3740f5910> is not bound to a Session; attribute refresh operation cannot proceed (Background on this error at: http://sqlalche.me/e/13/bhk3 )
2020-10-25 11:17:15,053 WARNI [fedora_messaging.twisted.protocol][MainThread] Returning message id c2d97737-444f-49b4-b4ca-1efb3a05e941 to the queue