CHROMIUM: Add logging for unset attribute while logging failure.

Add a log noting the missing package use flags and the object itself.
The error appears to happen only in slim builders while trying to
determine which packages to build, causing them to always fall back
to all packages.

BUG=b:223433932
TEST=CQ & check slim builders

Change-Id: I577b47fa8d5b144f25f65dde8155fe6f376fb3d0
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/portage_tool/+/3803728
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Auto-Submit: Alex Klein <saklein@chromium.org>
Tested-by: Alex Klein <saklein@chromium.org>
Commit-Queue: Alex Klein <saklein@chromium.org>
1 file changed