[depot_tools] Turn my_activity.py into a vpython script
[depot_tools] Turn my_activity.py into a vpython script

Downside: the script now requires "-u user@chromium.org" or it results
in "error: USER is not set, please use -u".

Bug: 904604
Change-Id: I241ad440d0cf1a495ce6f57e48ed49d9d90a49d9
Reviewed-on: https://chromium-review.googlesource.com/c/1442851
Reviewed-by: Robbie Iannucci <40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org>
Commit-Queue: Gabriel Charette <41ae41107f68c5f6cb83171614f7cf276b0b3572@chromium.org>

CoherentLabs/depot_tools,CoherentLabs/depot_tools