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: I5df2451f24721ed34ff8a0a91c76896083ed9a0c
Tested-by: Chris Sosa <>
Reviewed-by: David James <>
Commit-Ready: Chris Sosa <>
3 files changed