Upon success the result was correct but also included:
"errors": [
{
"message": "User Error: expected iterable, but did not find one
for field <SerializerMutation_Subclass>Payload.errors."
}
]
This seemed to be due to Payload.errors defaulting to graphene.List
rather than unset or None. Unsure what exactly changed with 2.x to break
this, so I welcome a better fix, but explicitly setting errors to None
also seems easy enough.