`subuser repair` returns success to the shell despite failure

[DEVoytas]

After adding own image iceweasel-vlc and failure to repair:

Observed:

$ subuser repair
Verifying subuser configuration.
Checking if images need to be updated or installed...
[...]
New images for the following subusers need to be installed:
iceweasel-vlc
Installing iceweasel-vlc ...
[...]
Building image failed.
status: 500
Reason: Internal Server Error
Images for the following subusers failed to build:
iceweasel-vlc
Verify complete.
$ echo $?
0 # indicates success

Expected:

$ echo $?
1 # or other non-zero value indicates failure

Version used:

$ subuser version | head -1
Subuser version: 0.6.2-dev-c04a1bad771e65f2f27f9fc216c49753fa554258