The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/chromite/+/296b41289472775fddbad3d4df465c502374a607

commit 296b41289472775fddbad3d4df465c502374a607
Author: Don Garrett <dgarrett@google.com>
Date: Tue Feb 06 03:08:30 2018

cros clean: Add autotest site-packages support.

Since build-externals installs things directly into the autotest
source tree, cros-clean should be able to clean them up. Add support
for that.

BUG= chromium:808246 
TEST=cros clean --autotest; cros clean --clobber

Change-Id: I1242b5b1ce0a6979bb1db90d77bc514fd020faa7
Reviewed-on: https://chromium-review.googlesource.com/898348
Commit-Ready: Don Garrett <dgarrett@chromium.org>
Tested-by: Don Garrett <dgarrett@chromium.org>
Reviewed-by: Allen Li <ayatane@chromium.org>

[modify] https://crrev.com/296b41289472775fddbad3d4df465c502374a607/cli/cros/cros_clean.py