I can't reproduce the error here giving a proof of concept, but this bug is only happening in production and is really confusing. Has anyone here in the Plone community had a similar problem somehow?
from plone.supermodel import model
class IMyField(model.Schema):
myfield = schema.Choice(
title=_(u'My Field'),
required=False,
description=_(u'MyField'),
vocabulary=my_fields,
)
{
"message": "[{'field': 'myfield', 'message': u'Required input is missing.', 'error': RequiredMissing('myfield')}]",
"type": "BadRequest"
}