Fix a python invocation that wasn't replaced with vpython.
Fix a python invocation that wasn't replaced with vpython.

This fixes autoninja on my Windows machine at home.

Bug: none
Change-Id: I3c245715c409bb2b30fcc3733bb097fc2a88f464
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2021755
Reviewed-by: Aaron Gable <bbed39beedae4cdb499af742d2fcd6c63934d93b@chromium.org>
Commit-Queue: Peter Kasting <af2833f195af96c34185f741f3f4394197a8590f@chromium.org>

CoherentLabs/depot_tools,CoherentLabs/depot_tools