permission: openapi.yml is not writable when installed as system package

In a docker context, the cube is installed as a system package and the openapi.yaml file is not writable

File "/usr/local/lib/python3.9/site-packages/cubicweb_api/openapi/openapi.py", line 53, in register_openapi_routes
generate_openapi_file(path_prefix)
File "/usr/local/lib/python3.9/site-packages/cubicweb_api/openapi/openapi.py", line 47, in generate_openapi_file
with open(get_file_in_folder(OpenApiFiles.production), "w") as file:
PermissionError: [Errno 13] Permission denied: '/usr/local/lib/python3.9/site-packages/cubicweb_api/openapi/openapi.yaml'
unable to load app 0 (mountpoint='') (callable not found or import error)