Mozilla cornice api request validation with Schematics model

validation.py

# coding: utf8

from schematics.models import ModelMeta
from schematics.exceptions import ModelValidationError


def validate_model(model):
    '''
    Validate cornice api request against given schematics `model`
    :param model: Schematics model
    '''
    if not isinstance(model, ModelMeta):
        raise Exception("model should be schematics model class")

    def validate(request):
        json_body = {}
        try:
            json_body = request.json_body
        except Exception as ex:
            # request.errors.add('body', None, 'Invalid request json')
            pass
        m = model(json_body)
        # Perform model validation
        try:
            m.validate()
        except ModelValidationError as validation_exc:
            for k, v in validation_exc.messages.items():
                request.errors.add('body', k, v)
    return validate

# Usage 
from cornice.service import Service
from schematics.models import Model
from schematics.types import StringType, BooleanType

# Define schema
class Category(Model):
    name = StringType(required=True, min_length=3, max_length=100)
    published = BooleanType(default=False)

# Define cornice api
category_coll_api = Service('category_coll_api_v1', path='/api/v1/category', renderer='json')

@category_coll_api.post(validators=[validate_model(Category)], http_cache=None)
def create_category(request):
    pass

# This will fail for request with improper data