[Python] rest_client.py does not accept byte types for body

Description

If I pre convert the body to be POST or PUT to an API into bytes from XML, like the following code based on an lxml parsed element:

from lxml import etree

# ... intervening code

el = # some lxml element
body = etree.tostring(el, encoding='utf-8')

I cannot then use this body with rest_client.py generated by the API client - it will only accept type str despite the fact that Python 2 is end-of-life.

Swagger-codegen version

3.0.24 or 3.0.25

Command line used for generation

I am working Ex Libris' Alma product which requires API keys. Not sure if this helps you but:

java -jar lib/swagger-codegen-cli.jar generate -l python -c api-config.json -i https://developers.exlibrisgroup.com/wp-content/uploads/alma/openapi/bibs.yaml --resolve-fully -o target

The api-config.json is below

{
  "packageName": "alma_api",
  "modelPackage": "models",
  "apiPackage": "apis"
}

Steps to reproduce

1. Take any API that accepts a PUT or a POST
2. Build a bytes type input for body
3. Use it with the API

Suggest a fix/enhancement

See the code for encoding the body in modules/swagger-codegen/src/main/resources/python/rest.mustache.

You can see that the default type expected for an encoded body is str, but in Python 3 it should be bytes.

There are a number of options here:

1. Drop support for Python 3 and simply accept either str or bytes
2. Split the Python code generator from Python 3- support Python 2 as legacy.
3. Use exception processing code to support both at the same time.

Because there are options around whether to support Python 2 going forward, it may be hard for a new contributor to craft a pull request until the need to support Python 2 going forward is solved.

I think Maven/Apache Ivy supplies the answer - if you need Python 2 support, use an older version.

Start with modules/swagger-codegen/src/main/resources/python/rest.mustache around the body-encoding code cited in the issue. Reproduce the failure using a Python bytes body with a generated client, then determine which Python 2 and Python 3 compatibility approach the project will accept. Done means the chosen behavior is implemented and bytes bodies work for POST or PUT requests without leaving the support policy unresolved.