>You can't. It wouldn't be completely impossible to add support for this,
>but it would need a nontrivial amount of work and make the code even
>more complicated (read the 'fetch' function in portage.py and you'll
>understand ;).
>  
>
are you sure that it would make the code even more complicated ?

i've read the function and it seems to be more or less just a reordering 
of the actions; something like:

- for packages with fetch restrictions, try local mirrors only
(for packages without the restriction, try local mirrors first, then 
official mirrors -> as it is now)

- if a file cannot be fetched and restriction flag is turned on, print 
message 'xyz has fetch restriction turned on ... bla bla ...' rather 
then complain about no mirrors available or downloadable problems
(if the restriction flag is not turned on, print the current message)

what do you think ?