aptitude won't return an error code when there is an error, it always return 0, why?

Some output from aptitude wouldn't go amiss. Would you care to post us some?
Cheers,
jdk

This basically is a local server to try out of installing myproject
debian package. After issuing the aptitude install, I unplug the network cable, it complain about can't get the package in the middle, but at the
end, everything went ok, so the return value is 0.

Thanks in advance if you can post an solution that we can get error code of non-zero.

Here is a log
------------------------------------------------------
root@Mymachine:~# aptitude -o Aptitude::Cmdline::ignore-trust-violations=true -y insttall myproject=1.0023-1
Reading package lists... Done
Reading state information... Done
Reading extended state information... Done
Initializing package states... Done
Building tag database... Done
The following packages are BROKEN:
myproject
0 packages upgraded, 0 newly installed, 1 downgraded, 1 to remove and 0 not upgraded.
Need to get 12.1MB of archives. After unpacking 0B will be used.

Score is 334

WARNING: untrusted versions of the following packages will be installed!

Untrusted packages could compromise your system's security.
You should only proceed with the installation if you are certain that
this is what you want to do.

myproject

*** WARNING *** Ignoring these trust violations because
aptitude::CmdLine::Ignore-Trust-Violations is 'true'!

Need to get 30.2MB of archives. After unpacking 0B will be used.
WARNING: untrusted versions of the following packages will be installed!

Untrusted packages could compromise your system's security.
You should only proceed with the installation if you are certain that
this is what you want to do.

myproject

*** WARNING *** Ignoring these trust violations because
aptitude::CmdLine::Ignore-Trust-Violations is 'true'!
Writing extended state information... Done
0% [Working] 0% [Connecting to 192.168.33.44 (192.168.33.44)]0% [Connecting to 192.168.33.44 (192.168.33.44)]0% [Connecting to 192.168.33.44 (192.168.33.44)]0% [Connecting to 192.168.33.44 (192.168.33.44)]0% [Connecting to 192.168.33.44 (192.168.33.44)]0% [Connecting to 192.168.33.44 (192.168.33.44)] Err http://192.168.33.44 tangerine/./ myproject 1.0023-1
Could not connect to 192.168.33.44:80 (192.168.33.44). - connect (113 No route to host)
0% [Working] E: Failed to fetch http://192.168.33.44/ubuntu/mydumb_p...023-1_all.deb: Could not connect to 192.168.33.44:80 (192.168.33.44). - connect (113 No route to host)
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done