[python-flask] Error when API path parameters include a dash character.

Description

Python does not allow to declare variables with a dash "-" character because its considered as a minus operation between two variables.

Thus when the python-flask codegen tools finds a paramter with a dash character in the swagger file, it is automatically translated into a lowbar character "_" into the output swagger.yaml file used for the code generation.

However the input parameter within the API entry URI remains unchanged with the dash character within, resulting into an inconsistency into the python server.

Example:

/data/context/connectivity-service={uuid}/cost-characteristic={cost-name}/:
    get:
      tags:
      - "tapi-connectivity"
      description: "returns tapi.topology.CostCharacteristic"
      parameters:
      - name: "uuid"
        in: "path"
        description: "Id of connectivity-service"
        required: true
        type: "string"
      - name: "cost-name"
        in: "path"
        description: "Id of cost-characteristic"
        required: true
        type: "string"

Error while executing the generated flask server:

python3 -m swagger_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 "/home/tid/proyecto/TAPIpythonServer/swagger_server/__main__.py", line 16, in <module>
    main()
  File "/home/tid/proyecto/TAPIpythonServer/swagger_server/__main__.py", line 11, in main
    app.add_api('swagger.yaml', arguments={'title': 'tapi-topology,tapi-common,tapi-path-computation,tapi-connectivity,tapi-otsi API'})
  File "/home/tid/.local/lib/python3.5/site-packages/connexion/apps/flask_app.py", line 54, in add_api
    api = super(FlaskApp, self).add_api(specification, **kwargs)
  File "/home/tid/.local/lib/python3.5/site-packages/connexion/apps/abstract.py", line 159, in add_api
    options=api_options.as_dict())
  File "/home/tid/.local/lib/python3.5/site-packages/connexion/apis/abstract.py", line 92, in __init__
    validate_spec(spec)
  File "/home/tid/.local/lib/python3.5/site-packages/swagger_spec_validator/validator20.py", line 97, in validate_spec
    validate_apis(apis, bound_deref)
  File "/home/tid/.local/lib/python3.5/site-packages/swagger_spec_validator/validator20.py", line 302, in validate_apis
    validate_unresolvable_path_params(api_name, all_path_params)
  File "/home/tid/.local/lib/python3.5/site-packages/swagger_spec_validator/validator20.py", line 523, in validate_unresolvable_path_params
    raise SwaggerValidationError(msg)
swagger_spec_validator.common.SwaggerValidationError: Path parameter 'topology-id' used is not documented on '/data/context/connection={uuid}/connection-end-point={topology-id},{node-id},{owned-node-edge-point-id},{connection-end-point-id}/'

Swagger-codegen version

swagger-codegen-cli-2.3.1

Start with the generated swagger.yaml and the generated main.py entry point shown in the traceback, then inspect how the Python-Flask generator handles dashed path parameters. Reproduce the failing app.add_api call with the provided path and verify that the generated specification and Flask server use consistent parameter names and start successfully.