Rename local variable with prefix "local_var_" in Python client

Description

We will need to rename the local variables in Python client with the prefix "local_var_" to avoid conflicts with the endpiont parameters or reserved keywords

e.g. renaming params to local_var_params in https://github.com/OpenAPITools/openapi-generator/blob/master/samples/client/petstore/python/petstore_api/api/pet_api.py

Swagger-codegen version

Latest master

Suggest a fix/enhancement

If anyone wants to work on this, please reply to let us know.

A good starting point it the mustache templates: https://github.com/OpenAPITools/openapi-generator/tree/master/modules/openapi-generator/src/main/resources/python