Add vpython to depot_tools for linux and mac
BUG=717208
R=dnj@chromium.org
Change-Id: If937a382be9aa4d8eb5f957386e8b1b28cc1c3ac
Reviewed-on: https://chromium-review.googlesource.com/492086
Reviewed-by: Daniel Jacques <dnj@chromium.org>
Reviewed-by: Nodir Turakulov <nodir@chromium.org>
Commit-Queue: Sergey Berezin <sergeyberezin@chromium.org>