v2 collection publish API raises exception

[sivel]

Version

pulp-ansible==0.17.0
pulpcore==3.23.3

Using the container from quay.io/pulp/galaxy

Describe the bug
When attempting to publish a collection to the v2 API endpoint /pulp_ansible/galaxy/<distro>/api/v2/collections/ an exception is raised:

Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.8/site-packages/django/core/handlers/base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/local/lib/python3.8/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/django/views/generic/base.py", line 70, in view
    return self.dispatch(request, *args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/views.py", line 509, in dispatch
    response = self.handle_exception(exc)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/views.py", line 469, in handle_exception
    self.raise_uncaught_exception(exc)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/views.py", line 480, in raise_uncaught_exception
    raise exc
  File "/usr/local/lib/python3.8/site-packages/rest_framework/views.py", line 506, in dispatch
    response = handler(request, *args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/pulp_ansible/app/galaxy/views.py", line 184, in post
    serializer.is_valid(raise_exception=True)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/serializers.py", line 227, in is_valid
    self._validated_data = self.run_validation(self.initial_data)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/serializers.py", line 430, in run_validation
    assert value is not None, '.validate() should return the validated data'
AssertionError: .validate() should return the validated data

To Reproduce
Attempt to publish collection to v2 API explicitly

Expected behavior
No traceback, collection published

Additional context
Add any other context about the problem here. Please provide links to any previous discussions via Discourse or Bugzilla.

#1432