Few crashes

[MKSG-MugunthKumar]

There are a few crashes in the app

1. Trying to convert an audiobook to MP3 before it is downloaded.
2. Trying to transcribe before a downloaded audiobook is converted to MP3

The app expects the flow to be
Authenticate Audible -> List Books -> Download Books -> Convert Books -> Transcribe Books -> Authenticate Readwise -> Post Highlights

If a step is missed, the app crashes.

Either we fix this or change the way the menu is displayed so that the crash is avoided.
For example: When the user runs the Convert Books command, show only the list of downloaded books or error out asking the user to download a book before proceeding.

Another option is to build a Django web UI and keep the command line interface only for developers.

Open to ideas/suggestions/pull requests!

@GGyll @JulianLagier

[GGyll]

Django UI sounds great and should be easy to implement.
For the CLI I think the easiest way is to dynamically show the help menu on each step like you suggested.

Are you able to work on the Django implementation?