With the mat-gui, when click on [Scour] after adding a file to clean, there's the following traceback :

Traceback (most recent call last):
  File "./mat-gui", line 419, in __mat_clean
    if self.liststore[line][0].file.remove_all(whitelist=list_to_add):
UnboundLocalError: local variable 'list_to_add' referenced before assignment

Nevertheless, the file seems to be cleaned after that.

(from redmine: created on 2014-01-19, closed on 2014-01-29)