The coming new version of Celery introduced a new behaviour
when calling apply_async [1]. It checks the task arguments.
This behaviour is not compatible when the design of
TrytonTask because it override the apply_async to add
transactional keyword arguments and those arguments are not
defined on the function of the Task.
I see three options to deal with this new behaviour:

- we could override the __header__ to remove the
transactional keywords.

- we could remove the __header__ and so the check will not
be done.

- we could require to write task function that takes keyword
arguments.

The first option is clearly the one that is the richer in
term of feature but it is also the more complex to implement.
The last option is the easiest but it will be complicate to
explain to users why they must put a keyword arguments that
are never used.

[1]
https://github.com/celery/celery/commit/3e91891c7b3abc8f68a65167c73e4bd895d2c497