Django json schema validator

json_schema_validator.py

import json
import os

from django.contrib.postgres.fields import JSONField
from django.core.exceptions import ValidationError
from django.utils.deconstruct import deconstructible
from jsonschema import validate, exceptions as jsonschema_exceptions


@deconstructible
class JSONSchemaValidator(JSONField):

    def __init__(self, *args   , **kwargs):
        schema = kwargs.pop('schema', None)
        if not schema:
            raise ValueError('Schema is required')
        if not isinstance(schema, str):
            raise TypeError('Schema must be a path string, ex: "schemas/media_effects_jsonschema.json"')

        self.schema = schema
        super().__init__(*args, **kwargs)

    @property
    def _schema_data(self):
        dirname = os.path.dirname(os.path.realpath(__file__))
        p = os.path.join(dirname, self.schema)
        with open(p, 'r') as read_file:
            return json.loads(read_file.read())

    def __call__(self, value):
        try:
            status = validate(json.loads(value), self._schema_data)
        except jsonschema_exceptions.ValidationError as err:
            error_msg = '{} {}.'.format(
                self.error_messages.get('invalid', str(err)),
                'Please check jsonschema'
            )
            raise ValidationError(error_msg)
        except ValueError as err:
            raise ValidationError('Field should be a valid json')
        return status