Celery error when using rabbitmq as broker

[ne018]

[2020-10-30 18:02:56,696: INFO/ForkPoolWorker-2] Task massmailer.tasks.send_email[massmailer-aeaa2e15-a1b6-4e78-8317-253a7f21654a] retry: Retry in 60s: TypeError("Object of type 'UUID' is not JSON serializable",)
[2020-10-30 18:02:56,698: INFO/MainProcess] Received task: massmailer.tasks.send_email[massmailer-aeaa2e15-a1b6-4e78-8317-253a7f21654a]  ETA:[2020-10-30 18:03:56.694045+00:00] 
[2020-10-30 18:03:56,843: WARNING/ForkPoolWorker-2] Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: Hi myemail@gmail.com
From: webmaster@localhost
To: myemail@gmail.com
Date: Fri, 30 Oct 2020 18:03:56 -0000
Message-ID: <160408103684.2439.2899414189599422213@ubuntu-bionic>
X-MID: aeaa2e15-a1b6-4e78-8317-253a7f21654a

Hello this is a test
[2020-10-30 18:03:56,843: WARNING/ForkPoolWorker-2] -------------------------------------------------------------------------------
[2020-10-30 18:03:56,861: ERROR/ForkPoolWorker-2] Task massmailer.tasks.send_email[massmailer-aeaa2e15-a1b6-4e78-8317-253a7f21654a] raised unexpected: TypeError("Object of type 'UUID' is not JSON serializable",)
Traceback (most recent call last):
  File "/home/vagrant/.local/lib/python3.6/site-packages/celery/app/trace.py", line 409, in trace_task
    R = retval = fun(*args, **kwargs)
  File "/home/vagrant/.local/lib/python3.6/site-packages/celery/app/trace.py", line 701, in __protected_call__
    return self.run(*args, **kwargs)
  File "/home/vagrant/.local/lib/python3.6/site-packages/massmailer/tasks.py", line 51, in send_email
    raise self.retry(exc=exc)
  File "/home/vagrant/.local/lib/python3.6/site-packages/celery/app/task.py", line 701, in retry
    raise_with_context(exc)
  File "/home/vagrant/.local/lib/python3.6/site-packages/massmailer/tasks.py", line 39, in send_email
    ret = python_mail.send(fail_silently=False)
  File "/home/vagrant/.local/lib/python3.6/site-packages/django/core/mail/message.py", line 284, in send
    return self.get_connection(fail_silently).send_messages([self])
  File "/home/vagrant/.local/lib/python3.6/site-packages/sendgrid_backend/mail.py", line 129, in send_messages
    resp = self.sg.client.mail.send.post(request_body=data)
  File "/home/vagrant/.local/lib/python3.6/site-packages/python_http_client/client.py", line 257, in http_request
    data = json.dumps(request_body).encode('utf-8')
  File "/usr/lib/python3.6/json/__init__.py", line 231, in dumps
    return _default_encoder.encode(obj)
  File "/usr/lib/python3.6/json/encoder.py", line 199, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/usr/lib/python3.6/json/encoder.py", line 257, in iterencode
    return _iterencode(o, 0)
  File "/usr/lib/python3.6/json/encoder.py", line 180, in default
    o.__class__.__name__)
TypeError: Object of type 'UUID' is not JSON serializable

It's working when im using simple custom task with send_mail but when sending batch mail from massmailer, it persist.

[ne018]

i solved it by converting id in model to string. str(self.id)