Don't show a stack trace when the archive file isn't found.
treec8ed715656d34cf954c7f65525a9aa9ee9981cbc
-rwxr-xr-x 6743 0publish
-rw-r--r-- 1130 0publish.xml
-rw-r--r-- 26536 COPYING
-rw-r--r-- 3507 archive.py
-rw-r--r-- 3185 create.py
-rw-r--r-- 1017 edit.py
-rw-r--r-- 1019 merge.py
-rw-r--r-- 2511 release.py
-rw-r--r-- 2605 signing.py
-rw-r--r-- 820 stable.py
-rw-r--r-- 4892 unpack.py
-rw-r--r-- 599 validator.py