Use explicit versioning with Python.

A new machine won't have `python` bound to anything.

Change-Id: I67ce37dea2ecfb3deaca4712804b04dc8d39ae36
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/736996
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
1 file changed