Fixes Issue 422, const in python

[spacether]

Fixes Issue 422, const in python

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• [ ] Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• [ ] Run the following to build the project and update samples:

  mvn clean package 
  ./bin/generate-samples.sh
  ./bin/utils/export_docs_generators.sh

  Commit all changed files. This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master. These must match the expectations made by your contribution. You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/generate_samples_configs/python* For Windows users, please run the script in Git BASH.

[spacether]

I verified that this fix works by sucessfully generating a python client using the openapi document from https://github.com/openapi-json-schema-tools/openapi-json-schema-generator/issues/442:

justinblack@Justins-MacBook-Air openapi-json-schema-generator % java -jar target/openapi-json-schema-generator-cli.jar generate \
   -i const_doc.json \
   -g python \
   -o ./out/
...
[main] INFO  o.o.c.templating.TemplateManager - writing file /Users/justinblack/programming/openapi-json-schema-generator/./out/.openapi-generator-ignore
[main] INFO  o.o.c.templating.TemplateManager - writing file /Users/justinblack/programming/openapi-json-schema-generator/./out/.openapi-generator/VERSION
[main] INFO  o.o.c.templating.TemplateManager - writing file /Users/justinblack/programming/openapi-json-schema-generator/./out/.openapi-generator/FILES
[main] INFO  o.o.c.g.DefaultGeneratorRunner - ################################################################################
[main] INFO  o.o.c.g.DefaultGeneratorRunner - # Thanks for using OpenAPI JSON Schema Generator.                              #
[main] INFO  o.o.c.g.DefaultGeneratorRunner - # Please consider donation to help us maintain this project 🙏                 #
[main] INFO  o.o.c.g.DefaultGeneratorRunner - # https://github.com/sponsors/spacether                                        #
[main] INFO  o.o.c.g.DefaultGeneratorRunner - ################################################################################