switch default SDK python to 3.6

Any scripts needing a specific version of Python should be using
`python2` in their shebang at this point.  Lets switch the default
over to Python 3 so we can prevent regressions.

TEST=SDK bot passes

Change-Id: Iff92e4b127aeb932c8c76dda2ae34a09f9e0c2ed
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/1757296
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
2 files changed