Throw multiple validation errors

multiple_exceptions.py

# based on http://stackoverflow.com/questions/6470428/catch-multiple-exceptions-in-one-line-except-block

class ValidationError(Exception):
    def __init__(self, attribute_name, message):
        self.attribute_name = attribute_name
        self.message = message
        
    def __str__(self):
        return self.message


class ValidationErrors(ValidationError):
    def __init__(self, errors*):
        self.attributes = []
        self.messages = []
        for error in errors:
            self.attributes.append(error.attribute_name)
            self.messages.append(error.message)

    def __str__(self):
        message = '['
        message += '; '.join(str(a) for a in self.attributes)
        message += ']'
        # this is for attribute names as a string list
        # return message
        # 
        # this is for std error messages
        return ' '.join(str(m) for m in self.messages)


e1 = ValidationError('AttributeA', 'Error 1.')
e2 = ValidationError('AttributeB', 'Error 2.')
# errors = [e1, e2]
raise ValidationErrors(e1, e2)
# Run and see "Error 1. Error 2." as error message