There is stacktrace all over the place about refusing to msgpack deserialization [1] for
some reason. Our default configuration is supposed to already allow it.
The doc says it supports both the name and the mimetype [2].
So as a tryout/short in the dark, here we go.
It's not tested though.
[1]
ContentDisallowed('Refusing to deserialize untrusted content of type msgpack (application/x-msgpack)')
[2] https://docs.celeryproject.org/en/stable/userguide/configuration.html#std-setting-accept_content
Related to T3632