I revoked listenbrainz access from my spotify preferences page, and shortly after received an email from LB:

Hi!

We encountered an error while importing your listens from Spotify.
The error was as follows: "('Error from the Spotify API while getting listens: %s', 'http status: 403, code:-1 - https://api.spotify.com/v1/me/player/currently-playing:\n User not registered in the Developer Dashboard, reason: None')"

Please take a look at your Spotify import page (https://listenbrainz.org/profile/music-services/details/)
for more information.

Good to receive the email, but the formatting of the error message leaves something to be desired... This should be cleaned up