I use Band-in-a-box ("BIAB") to create backing tracks to practice my guitar-playing, and keep the source files (filetype .MGU) created by BIAB in the same folder as the MP3 files derived from them. Because I share this folder with colleagues via Dropbox, I'm not in a position to move the .MGU files elsewhere.

Every time I start Rhythmbox ("RB") it checks my music folders, and reports "Import Errors" on all the .MGU files.

RB apparently ignores a number of unplayable filetypes in music folders - is there a way of adding .MGU to this group?

I know I can just ignore the Import Errors, but one of these days there will be an error I would have wanted to know about.