if a filename ends with `.py` and the file begins with '#!.*python.*',
make it executable.
Change-Id: I41de516ff37343d3b0979bde9fd61813aec7365c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/254439
Commit-Queue: Hal Canary <halcanary@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
Auto-Submit: Hal Canary <halcanary@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
