Don't include archive diectories that are missing an when calculating previous image.

This change allows for a previous archive directory to be devoid of an
without throwing an exception when generating delta payloads. Sometimes we might
be missing an directory if the state of the last build was bad i.e. it
was aborted midstream -- archive directory is created but doesn't finish
getting generated.

I've also updated a lot of the logging/docstring to make clear what's happening
in image_extractor.

TEST=Unittests + pylint + running with full_suite w/ and w/out in latest.

Change-Id: Ie1719e30a7c96283e6d8384719d000fb86c83984
Reviewed-by: Chris Sosa <>
Tested-by: Chris Sosa <>
3 files changed