celery+kombu not giving a useful traceback - how to expand it?

I'm working on porting some Python 2.7 code to 3.10 (I know, it's late).

The server-side code uses:

celery==5.2.3
kombu==5.2.4

...though the client side is on something much older:

celery==3.1.26.post2
kombu==3.0.37

It appears that the server-side Celery or Kombu (they both can output the relevant error message), I don't know which, is giving a very terse traceback that I'd love to expand:

body: b'\x80\x02}q\x01(U\x07expires... (64915309b)
Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/celery/worker/consumer/consumer.py", line 568, in on_task_received
    type_ = message.headers['task']  # protocol v2
KeyError: 'task'

(I shortened the binary data a little myself on the "body" above)

My question is, how can I find out what part of my code is triggering that traceback?

Thanks!