run some tests using python3

Bug: 941669
Change-Id: Ib63daab2a4cb3868cfc37121c3f48ebb2019af39
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3301620
Auto-Submit: Takuto Ikuta <tikuta@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#945345}
NOKEYCHECK=True
GitOrigin-RevId: 658f361a34e21b92902a6b4c74047363b053cad3