Pgadmin3 error - FATAL: role "musicbrainz" does not exist

I don’t have an answer to your question, but feel like you could help me with my problem. I have been trying to access the database on my Mac with a GUI, but failed so far. You mention that you made it work on your Mac. Could you maybe guide me through the steps you took to make it work? Thanks.

More info on my problem in this post: Help extracting data from database (for academic research)