[Python][flask]Codegen for python-flask not generating model files

Description

Java-flask code files are not getting generated.
Running the command:
java -jar ~/swagger-codegen-cli-2.2.1.jar generate -i http://petstore.swagger.io/v2/swagger.json -l python-flask -o generated/test

gives the following response:
[main] INFO io.swagger.parser.Swagger20Parser - reading from http://petstore.swagger.io/v2/swagger.json
[main] INFO io.swagger.codegen.AbstractGenerator - writing file generated/test/swagger/swagger.yaml
[main] INFO io.swagger.codegen.AbstractGenerator - writing file generated/test/app.py
[main] INFO io.swagger.codegen.AbstractGenerator - writing file generated/test/README.md
[main] INFO io.swagger.codegen.AbstractGenerator - writing file generated/test/init.py
[main] INFO io.swagger.codegen.AbstractGenerator - writing file generated/test/controllers/default_controller.py
[main] INFO io.swagger.codegen.AbstractGenerator - writing file generated/test/controllers/init.py
[main] INFO io.swagger.codegen.AbstractGenerator - writing file generated/test/LICENSE

It seems to be missing the controller and model files.

Swagger-codegen version

2.2.1. Downloaded jar file as well as full build gives the same result

Swagger declaration file content or url

The petstore example itself does not work. http://petstore.swagger.io/v2/swagger.json

Command line used for generation

java -jar ~/swagger-codegen-cli-2.2.1.jar generate -i http://petstore.swagger.io/v2/swagger.json -l python-flask -o generated/test

Steps to reproduce

wget https://oss.sonatype.org/content/repositories/releases/io/swagger/swagger-codegen-cli/2.2.1/swagger-codegen-cli-2.2.1.jar
mkdir generated
java -jar ~/swagger-codegen-cli-2.2.1.jar generate -i http://petstore.swagger.io/v2/swagger.json -l python-flask -o generated/test

Related issues/PRs

Suggest a fix/enhancement

Please tell me what I am missing or is there a workaround?

Run the provided swagger-codegen-cli 2.2.1 command against the petstore Swagger URL and inspect the generated/test output, especially the controllers and model files. Compare the output with the schema's defined models and determine why model files are absent; done means the Python-Flask generation produces the expected model files as well as the existing controller files.