Propagate the error message to the user when updating bugzilla overrides
    
    Up until now the error message was hidden in the web console... not very
    nice for the users.
    Now we include the error message(s) in the pop-up shown to the user if
    updating the bugzilla overrides failed.
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>