client: support python3 in isolate_smoke_test.py
client: support python3 in isolate_smoke_test.py

but skip failed tests.

Bug: 1010816, 1101705
Change-Id: Id57656b67042059f5f36676aa26c42e2229810bb
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/2278906
Commit-Queue: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>
Reviewed-by: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>
Auto-Submit: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>

luci/luci-py,luci/luci-py,luci/luci-py,luci/luci-py