[BUG] [python-flask] Trying to run installed module NotADirectory error for yaml file

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Bounty to sponsor the fix (example)

Description

Using petstore swagger yaml I have created python-flask server. and then I have created dist and installed it.

python setup.py sdist
sudo python3 setup.py install
sudo python3 -m openapi_server

Trying to run the module and get the following error

sudo python3 -m openapi_server
Traceback (most recent call last):
  File "/usr/lib/python3.5/runpy.py", line 184, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/lib/python3.5/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/usr/local/lib/python3.5/dist-packages/openapi_server-1.0.0-py3.5.egg/openapi_server/__main__.py", line 18, in <module>
  File "/usr/local/lib/python3.5/dist-packages/openapi_server-1.0.0-py3.5.egg/openapi_server/__main__.py", line 13, in main
  File "/usr/local/lib/python3.5/dist-packages/connexion-2.4.0-py3.5.egg/connexion/apps/flask_app.py", line 54, in add_api
    api = super(FlaskApp, self).add_api(specification, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/connexion-2.4.0-py3.5.egg/connexion/apps/abstract.py", line 155, in add_api
    options=api_options.as_dict())
  File "/usr/local/lib/python3.5/dist-packages/connexion-2.4.0-py3.5.egg/connexion/apis/abstract.py", line 73, in __init__
    self.specification = Specification.load(specification, arguments=arguments)
  File "/usr/local/lib/python3.5/dist-packages/connexion-2.4.0-py3.5.egg/connexion/spec.py", line 151, in load
    return cls.from_file(spec, arguments=arguments)
  File "/usr/local/lib/python3.5/dist-packages/connexion-2.4.0-py3.5.egg/connexion/spec.py", line 107, in from_file
    spec = cls._load_spec_from_file(arguments, specification_path)
  File "/usr/local/lib/python3.5/dist-packages/connexion-2.4.0-py3.5.egg/connexion/spec.py", line 91, in _load_spec_from_file
    with specification.open(mode='rb') as openapi_yaml:
  File "/usr/lib/python3.5/pathlib.py", line 1151, in open
    opener=self._opener)
  File "/usr/lib/python3.5/pathlib.py", line 1005, in _opener
    return self._accessor.open(self, flags, mode)
  File "/usr/lib/python3.5/pathlib.py", line 371, in wrapped
    return strfunc(str(pathobj), *args)
NotADirectoryError: [Errno 20] Not a directory: '/usr/local/lib/python3.5/dist-packages/openapi_server-1.0.0-py3.5.egg/openapi_server/openapi/openapi.yaml'

openapi-generator version

openapi-generator-cli-4.2.0.jar

OpenAPI declaration file content or url

https://github.com/OAI/OpenAPI-Specification/blob/master/examples/v2.0/yaml/petstore.yaml

Command line used for generation

java -jar openapi-generator-cli-4.2.0.jar generate -i ./swagger.yaml -g python-flask -o generated/server/python/flask -c python-config.json

{
    "packageName": "openapi_server",
    "controllerPackage": "controllers",
    "defaultController": "default_controller",
    "sortParamsByRequiredFlag": true,
    "ensureUniqueParams": true,
    "allowUnicodeIdentifiers": false,
    "prependFormOrBodyParameters": false,
    "packageVersion": "1.0.0",
    "supportPython2": true,
    "serverPort": 9898
}

Steps to reproduce

python setup.py sdist
sudo python3 setup.py install
sudo python3 -m openapi_server

Related issues/PRs

Suggest a fix

I am new to python but maybe instead of trying to open yaml file as a file use ziputils to open a file inside an archive?

Start by reproducing the installation and module invocation with the generated python-flask server, then inspect openapi_server/main.py and the package produced by setup.py. Compare the installed path in the traceback with the generated distribution layout. Done means the installed openapi_server module starts without the NotADirectoryError when loading openapi.yaml.