Byte length not calculated correctly in python

Description

In our swagger declaration, we defined a property of type string and format bytes. We also specified that it should be between 15 and 16 bytes in length, like "AAAAAAAAAAAAAAAAAAAAAA==". When using our service as a REST API and sending it through our swagger page, strings like the example before work correctly. However, when trying to use the python client, and send in the string "AAAAAAAAAAAAAAAAAAAAAA==", it checks the string character length (24), instead of the byte length (16). If we try to send in something other than a string, it fails the regular expression check. Basically, the python generated code is incorrectly checking the length of bytes by looking at string length.

Swagger-codegen version

2.2.3

Swagger declaration file content or url

lte_subscription:
    type: object
    required:
      - auth_key
    properties:
      auth_key:
        type: string
        format: byte
        x-nullable: true
        minLength: 15
        maxLength: 16
        example: "AAAAAAAAAAAAAAAAAAAAAA=="

Command line used for generation

Generated into python

Steps to reproduce

if you call

import swagger_client
lte = swagger_client.LteSubscription(auth_key="AAAAAAAAAAAAAAAAAAAAAA==")

Related issues/PRs

Checked, and couldn't find anything

Suggest a fix/enhancement

in the generated code, it currently is:

@auth_key.setter
    def auth_key(self, auth_key):
        """
        Sets the auth_key of this LteSubscription.

        :param auth_key: The auth_key of this LteSubscription.
        :type: str
        """
        if auth_key is None:
            raise ValueError("Invalid value for `auth_key`, must not be `None`")
        if auth_key is not None and len(auth_key) > 16:
            raise ValueError("Invalid value for `auth_key`, length must be less than or equal to `16`")
        if auth_key is not None and len(auth_key) < 15:
            raise ValueError("Invalid value for `auth_key`, length must be greater than or equal to `15`")
        if auth_key is not None and not re.search('^(?:[A-Za-z0-9+\/]{4})*(?:[A-Za-z0-9+\/]{2}==|[A-Za-z0-9+\/]{3}=)?$', auth_key):
            raise ValueError("Invalid value for `auth_key`, must be a follow pattern or equal to `/^(?:[A-Za-z0-9+\/]{4})*(?:[A-Za-z0-9+\/]{2}==|[A-Za-z0-9+\/]{3}=)?$/`")

        self._auth_key = auth_key

but it should be this. Considering it requires a base64 encoded string, it should check the length of the base 64 decoding.

import base64

@auth_key.setter
    def auth_key(self, auth_key):
        """
        Sets the auth_key of this LteSubscription.

        :param auth_key: The auth_key of this LteSubscription.
        :type: str
        """
        param_length = len(base64.b64decode(auth_key))
        if auth_key is None:
            raise ValueError("Invalid value for `auth_key`, must not be `None`")
        if auth_key is not None and len(param_length) > 16:
            raise ValueError("Invalid value for `auth_key`, byte length must be less than or equal to `16`")
        if auth_key is not None and len(param_length) < 15:
            raise ValueError("Invalid value for `auth_key`, byte length must be greater than or equal to `15`")
        if auth_key is not None and not re.search('^(?:[A-Za-z0-9+\/]{4})*(?:[A-Za-z0-9+\/]{2}==|[A-Za-z0-9+\/]{3}=)?$', auth_key):
            raise ValueError("Invalid value for `auth_key`, must be a follow pattern or equal to `/^(?:[A-Za-z0-9+\/]{4})*(?:[A-Za-z0-9+\/]{2}==|[A-Za-z0-9+\/]{3}=)?$/`")

        self._auth_key = auth_key

Start with the generated Python model setter shown in the issue and trace it back to the Python client-generation template or entry point. Reproduce the lte_subscription auth_key case with minLength 15 and maxLength 16, then verify the generated client accepts the 16-byte base64 value and rejects values outside the declared byte range.