Improve upload_to_google_storage.py missing file handling
Improve upload_to_google_storage.py missing file handling

When there are missing input files, upload_to_google_storage.py
should not display 'Success'.

Bug: 920654
Change-Id: I1bc7ba6e8eb48ea28b634da01e1be9a80af7b719
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2647870
Reviewed-by: Dirk Pranke <6693ee08b084bb2ffa767f664c99b689395e0e4b@google.com>
Commit-Queue: John Chen <334fbfbb4df7c78f091ea1b77c69ca6ac731a3f3@chromium.org>

CoherentLabs/depot_tools,CoherentLabs/depot_tools