[PYTHON] Issue #2028 - additionalProperties support

[ivan-gomes]

PR checklist

• Read the contribution guidelines.
• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh and ./bin/security/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\.
• Filed the PR against the correct branch: master, 3.4.x, 4.0.x. Default: master.
• Copied the technical committee to review the pull request if your PR is targeting a particular programming language.

Description of the PR

Fixes #2028. Adapted from accepted PR swagger-api/swagger-codegen#8414.

@taxpon @frol @mbohlool @cbornet @kenjones-cisco @tomplus @Jyhess

[wing328]

@ivan-gomes thanks for the PR but the Travis CI reports the following errors:

======================================================================
ERROR: Failure: NameError (name 'Animal' is not defined)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/travis/build/OpenAPITools/openapi-generator/samples/client/petstore/python/.tox/py27/local/lib/python2.7/site-packages/nose/loader.py", line 418, in loadTestsFromName
    addr.filename, addr.module)
  File "/home/travis/build/OpenAPITools/openapi-generator/samples/client/petstore/python/.tox/py27/local/lib/python2.7/site-packages/nose/importer.py", line 47, in importFromPath
    return self.importFromDir(dir_path, fqname)
  File "/home/travis/build/OpenAPITools/openapi-generator/samples/client/petstore/python/.tox/py27/local/lib/python2.7/site-packages/nose/importer.py", line 94, in importFromDir
    mod = load_module(part_fqname, fh, filename, desc)
  File "/home/travis/build/OpenAPITools/openapi-generator/samples/client/petstore/python/test/test_mixed_properties_and_additional_properties_class.py", line 17, in <module>
    import petstore_api
  File "/home/travis/build/OpenAPITools/openapi-generator/samples/client/petstore/python/petstore_api/__init__.py", line 20, in <module>
    from petstore_api.api.another_fake_api import AnotherFakeApi
  File "/home/travis/build/OpenAPITools/openapi-generator/samples/client/petstore/python/petstore_api/api/__init__.py", line 6, in <module>
    from petstore_api.api.another_fake_api import AnotherFakeApi
  File "/home/travis/build/OpenAPITools/openapi-generator/samples/client/petstore/python/petstore_api/api/another_fake_api.py", line 20, in <module>
    from petstore_api.api_client import ApiClient
  File "/home/travis/build/OpenAPITools/openapi-generator/samples/client/petstore/python/petstore_api/api_client.py", line 26, in <module>
    import petstore_api.models
  File "/home/travis/build/OpenAPITools/openapi-generator/samples/client/petstore/python/petstore_api/models/__init__.py", line 24, in <module>

Full log: https://travis-ci.org/OpenAPITools/openapi-generator/builds/486718967

Would you please take a look?

Also please run ./bin/python-petstore-all.sh to update the Python samples for asyncio and tornado

[spacether]

@ivan-gomes what's the status on this PR?
Do you still want to merge it?

The python-experimental generator now supports additional properties.
ample tests:

• https://github.com/OpenAPITools/openapi-generator/blob/master/samples/client/petstore/python-experimental/test/test_additional_properties_object.py
• https://github.com/OpenAPITools/openapi-generator/blob/master/samples/client/petstore/python-experimental/tests/test_deserialization.py#L380

[spacether]

@ivan-gomes thank you for this PR.
I am working on cleaning up old python PRs.
Do you still want to merge this?
If so, can you resolve the test failures?
If not, can you close it?

[ivan-gomes]

Closed in favor of #2049.