We were attempting to run pylint-2.6 with python2, when
it needs to be run with python3. I'm not sure how we
haven't noticed this before now.

Bug: 1157676
Change-Id: I60fc22a805c20649d04f7d0f53c828a0db41e8e7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3068833Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Reviewed-by: Peter Wen <wnwen@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@google.com>