[CT] mock is now a required python package on CT swarming bots
[CT] mock is now a required python package on CT swarming bots

Bug: skia:8407
Change-Id: Ic53adb9d450a3ec1b0d5eb5ee6e6a121d5843809
Reviewed-on: https://skia-review.googlesource.com/156229
Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>
Commit-Queue: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot