Revert^2 "Port Checker to python 3"

This reverts commit 5409408a41045c7f178e362311eb51dab992d6db.

Reason for revert: The original issue (b/170308859) is fixed by
https://android-review.googlesource.com/c/platform/art/+/1458282.

Test: art/tools/checker/run_unit_tests.py
Test: art/test/testrunner/testrunner.py --host
Bug: 170308859
Bug: 162408889

Change-Id: Ibc4539403ea77a9e718c830466459e6354ef0f23
10 files changed