version 2.7.2-1 on debian testing
A CD with a stub only (i.e. not a full MusicBrainz record) will throw an error. I don't know if enough information is returned from MusicBrainz for a stub to continue on or if abcde would have to give up anyway, but the exception is confusing, especially the first time. This is the session for "Captain & Tennille" "Love Will Keep Us Together". By the time you get to this I will probably have created a full record for this, so I can't provide you with a reproduction.
session showing the exception:
Executing customizable pre-read function... done.
Getting CD track info... Querying the CD for audio tracks...
Grabbing entire CD - tracks: 01 02 03 04 05 06 07 08 09 10 11
Obtaining Musicbrainz results...
Can't call method "events" on an undefined value at /usr/bin/abcde-musicbrainz-tool line 98.
No CDDB information found, trying cdtext from the CD
No Musicbrainz match.
---- Unknown Artist / Unknown Album ----
1: Track 1
2: Track 2
3: Track 3
4: Track 4
5: Track 5
6: Track 6
7: Track 7
8: Track 8
9: Track 9
10: Track 10
11: Track 11
Edit selected CDDB data [Y/n]? ^C
euterpe@euterpe:~/Music$ rm -r abcde.prVpjA9r6t5L2nttPy3Zll0nkW4-/
Thanks for the report. I've already added guarding in this area for CD releases without year data. I'll add more to look if events even exist too!
Fix released in 2.8