Enable python3 on some LUCI builds. am: 1ae8925233 am: a42c0b7245 am: c0ebcb19a8 am: e530f20406 am: 63e45c1b1b

Original change: https://android-review.googlesource.com/c/platform/art/+/2067139

Change-Id: I20eb523f059b4f30a4f16786313af7d28726418b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>