Script is dead for now. See this thread: Discogs images
Discogs have changed their website code for the release pages. In the above thread there are also links to the Discogs forum pages discussion (second post)
The worrying thing is I can’t see how the script can be fixed for larger releases as they are now breaking releases into pages of 25 tracks 
Seems a very backwards design in many ways and causing a lot of problems in the Discogs thread