Bug when creating a session using the REST API without specifying the users

[rossant]

When creating a session using the REST API without specifying the users, this error occurs:

[Errno 500] /sessions: 'Traceback (most recent call last):
  File "/var/www/alyx-test/venv/lib/python3.8/site-packages/rest_framework/views.py", line 506, in dispatch
    response = handler(request, *args, **kwargs)
  File "/var/www/alyx-test/venv/lib/python3.8/site-packages/rest_framework/generics.py", line 246, in post
    return self.create(request, *args, **kwargs)
  File "/var/www/alyx-test/venv/lib/python3.8/site-packages/rest_framework/mixins.py", line 19, in create
    self.perform_create(serializer)
  File "/var/www/alyx-test/venv/lib/python3.8/site-packages/rest_framework/mixins.py", line 24, in perform_create
    serializer.save()
  File "/var/www/alyx-test/venv/lib/python3.8/site-packages/rest_framework/serializers.py", line 208, in save
    self.instance = self.create(validated_data)
  File "/var/www/alyx-test/venv/lib/python3.8/site-packages/rest_framework/serializers.py", line 1014, in create
    field.set(value)
  File "/var/www/alyx-test/venv/lib/python3.8/site-packages/django/db/models/fields/related_descriptors.py", line 1209, in set
    objs = tuple(objs)
TypeError: 'LabMember' object is not iterable
'

I wonder if the problem is not on this line where the default users should actually be a list with a single element [serializers.CurrentUserDefault()] instead of just serializers.CurrentUserDefault().