IsADirectoryError: [Errno 21] Is a directory: '/.secrets/client_secret.json'

[todsandberg]

I was very excited when I found your project and have been trying to get it to work. I've overcome many issues, but now I'm stuck.

I was able to build it (on windows 10)
however when I try to run the following command I get the error below.

docker run -v /doc2audiobook/data:/data:rw -v /doc2audiobook/.secrets/client_secret.json:/.secrets/client_secret.json:ro doc2audiobook -list-voices

Traceback (most recent call last):
  File "/code/doc2audiobook/doc2audiobook.py", line 111, in <module>
    main()
  File "/code/doc2audiobook/doc2audiobook.py", line 77, in main
    client = texttospeech.TextToSpeechClient()
  File "/usr/local/lib/python3.7/site-packages/google/cloud/texttospeech_v1/gapic/text_to_speech_client.py", line 159, in __init__
    address=api_endpoint, channel=channel, credentials=credentials
  File "/usr/local/lib/python3.7/site-packages/google/cloud/texttospeech_v1/gapic/transports/text_to_speech_grpc_transport.py", line 61, in __init__
    channel = self.create_channel(address=address, credentials=credentials)
  File "/usr/local/lib/python3.7/site-packages/google/cloud/texttospeech_v1/gapic/transports/text_to_speech_grpc_transport.py", line 91, in create_channel
    address, credentials=credentials, scopes=cls._OAUTH_SCOPES, **kwargs
  File "/usr/local/lib/python3.7/site-packages/google/api_core/grpc_helpers.py", line 177, in create_channel
    credentials, _ = google.auth.default(scopes=scopes)
  File "/usr/local/lib/python3.7/site-packages/google/auth/_default.py", line 305, in default
    credentials, project_id = checker()
  File "/usr/local/lib/python3.7/site-packages/google/auth/_default.py", line 165, in _get_explicit_environ_credentials
    os.environ[environment_vars.CREDENTIALS])
  File "/usr/local/lib/python3.7/site-packages/google/auth/_default.py", line 91, in _load_credentials_from_file
    with io.open(filename, 'r') as file_obj:
IsADirectoryError: [Errno 21] Is a directory: '/.secrets/client_secret.json'

Could you give me a clue to what I'm doing wrong?
I wanted to look inside the code, but I'm not sure how to access it. I'm assuming it's within the docker, but I don't know how to get to the file in order to view it (for example google/auth/_default.py).

Perhaps I didn't create the json file correctly? I tried multiple versions. I'm new to GCP.

I'm really hoping you can help me figure this out.
The wavnet voices seem great and I'd love to convert an epub file into mp3(s)

Thank you