autoupdate: Fix unittest + update to python3

BUG=none
TEST=./run_unittests

Change-Id: I8e6bd80fe4ca265afd6a8beec7349002bfd6b007
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/3273333
Tested-by: Jae Hoon Kim <kimjae@chromium.org>
Reviewed-by: Jaques Clapauch <jaquesc@google.com>
Commit-Queue: Jae Hoon Kim <kimjae@chromium.org>
1 file changed