Help users know what's wrong if they make the natural mistake of using a Spotiify URI instead of a Spotify link

[pbx]

Thanks for the software! I'm offering this PR as a possible UX improvement.

I made this mistake when I was trying out this app for the first time today. Running current master (44cf2d3), here's the output you get if you provide a Spotify URI like spotify:playlist:0wMH0M981nj70CQLzF1CzJ instead of a "Spotify link" as they call them:

Starting spotify_dl
Traceback (most recent call last):
  File ".../bin//spotify_dl", line 8, in <module>
    sys.exit(spotify_dl())
  File ".../spotify_dl/spotify_dl.py", line 69, in spotify_dl
    valid_item = validate_spotify_url(args.url)
  File ".../spotify_dl/spotify.py", line 90, in validate_spotify_url
    item_type, item_id = parse_spotify_url(url)
  File ".../spotify_dl/spotify.py", line 64, in parse_spotify_url
    item_id = parsed_url.split("/")[1]
IndexError: list index out of range
Sentry is attempting to send 0 pending error messages
Waiting up to 2 seconds
Press Ctrl-C to quit

I figured a one-line error message would be more helpful and friendly.

[pbx]

Hrm, at first read-through I'm not sure why this change is causing those test failures. I'll check it out if I get some more free time.

[SathyaBhat]

Hi @pbx thanks for the PR! The tests pass locally, I think its more of something to do with spotify rejecting credentials when coming in from Github actions - the same creds work locally. I'll try to take a look at it in a separate PR, for now I will merge it.

Thanks again for your contribution