Add logging to package_index.py
Add logging to package_index.py

The step that executes this step takes approximately 90 minutes, and it is
currently killed after 20 minutes of no output. Therefore add some progress
logging.

BUG=429684

Review URL: https://codereview.chromium.org/878313002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@293830 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build