Hi,
this should say it all, and the ticket has more information:
commit 39bce1410795c11b3b4dca83f64c9c8ef787c973
Author: intrigeri <intrigeri@???>
Date:   Wed Jul 8 18:55:47 2015 +0000
    Fix panic mode on MAC spoofing failure, bis repetita.
    
    In the past, we had "exit 1" in there. This problem was identified (#8571) and
    fixed (commit 1b46b5b) in Tails 1.2.3, by replacing this "exit 1"
    with "return 1".
    
    Then, while working on another, minor problem (#8687), the "exit 1" was
    reintroduced (commit 4ea050a) in Tails 1.3.2, presumably because we pasted
    sample code from the ticket, that had been drafted *before* #8571 was fixed.
    Sadly, nobody noticed in time.
    
    I cannot easily reproduce the bug on Tails/Wheezy (because I lack hardware whose
    MAC address fails to be spoofed there), but I could reproduce it with
    Tails/Jessie ("thanks" to the fact we're currently shipping the buggy 'wl'
    kernel module in there).
    
    Will-Fix: #9531
Cheers,
-- 
intrigeri