Reliably detect if a command line asset server update succeeded

I'm in the process of scripting some asset bundle builds from the command line. The idea is pretty simple. Update the assets from the asset server using the appropriate command line arguments, and after that invoke my asset bundle build script from the command line to build the bundles.

This all works peachy, unless ... It happens on occasion that the asset server becomes unresponsive. Or there is another kink somewhere down the line that causes the update process to fail. Ship happens.

The problem is that essentially there doesn't seem to be anything in the command line that notifies me that something has failed. And the log doesn't really provide any clear-cut information on success/failure/status either. In fact, it seems to cheerfully indicate that everything completed successfully even if it doesn't.

Is there any way in which I can reliably detect whether or not my asset server update succeeded, before I go on to try and build asset bundles?