Custom exception

exceptions.py

class BaseCustomerError(Exception):
    """Basic error for all Customer errors."""
    pass


class CreateNewStepError(BaseCustomerError):
    """Exception raised when trying to create a new CustomerStep.

    Attributes:
        message -- explanation of the error
        code -- code of the error
        customer -- customer of the current CustomerStep instance
        step -- current step of the CustomerStep instance
    """

    def __init__(self, message, customer, step):
        super(CreateNewStepError, self).__init__(message, customer, step)
        self.message = message
        self.customer = customer
        self.step = step
        self.code = 1

    def __str__(self):
        message = (f'It is not possible to create a new CustomerStep with'
                   'Step {self.step} and Customer {self.customer}')
        return message