When running presubmits you can tell if Python 2 presubmits are running,
but it's subtle, and it isn't obvious which presubmits are running under
Python 2.

This makes it obvious by always printing the path to PRESUBMIT.py
scripts that are run under Python 2. This change also fixes a bug in the
--verbose logic - it would print that a script was running before
evaluating _ShouldRunPresubmit.

Bug: 1352347
Change-Id: I45213acdb3b37f7be0713e5caba775841704817c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3826917
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>
Reviewed-by: Aravind Vasudevan <aravindvasudev@google.com>