vpython_wrapper: new wrapper entry point

This is Python 2 wrapper for use in older branches.

BUG=chromium:1196328
TEST=`./bin/cros_sdk` in old firmware branch works

Change-Id: I2a81191db4b77ccaab7c92c33508faccce0e6d25
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2893104
Commit-Queue: LaMont Jones <lamontjones@chromium.org>
Reviewed-by: LaMont Jones <lamontjones@chromium.org>
Tested-by: LaMont Jones <lamontjones@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/3040610
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Greg Edelston <gredelston@google.com>
Commit-Queue: Greg Edelston <gredelston@google.com>
3 files changed