Validate
        Perform value validation and return result

        :param value:           value to check
        :param model:           parent model being validated
        :param context:         object or None, validation context
        :return:                shiftschema.results.SimpleResult

def validate(self, value, model=None, context=None):
        """
        Validate
        Perform value validation and return result

        :param value:           value to check
        :param model:           parent model being validated
        :param context:         object or None, validation context
        :return:                shiftschema.results.SimpleResult
        """

        regex = self.regex()
        match = regex.match(value)
        if not match:
            return Error(self.not_email)

        # success otherwise
        return Error()