We're looking at dropping Python 3.5 support from repo.  Lets roll
this back out in Chromium a little early to get a better idea of
who is still relying on it.

Change-Id: Idcdd5b0a957f5a2f8b146149c407c26347be0aa5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2830590Reviewed-by: Stephane Belmon <sbelmon@google.com>
Commit-Queue: Mike Frysinger <vapier@chromium.org>