Avoid imports from Sugar shell

[quozl]

Two imports of jarabe are present. They should be avoided if possible.

On a system with Python 3 Sugar shell and Python 2 bundle of Pippy, the activity fails to start with this in logs;

Traceback (most recent call last):
  File "/usr/bin/sugar-activity", line 5, in <module>
    activityinstance.main()
  File "/usr/lib/python2.7/dist-packages/sugar3/activity/activityinstance.py", line 179, in main
    module = __import__(module_name)
  File "/usr/share/sugar/activities/Pippy.activity/pippy_app.py", line 76, in <module>
    from jarabe.view.customizebundle import generate_unique_id
ImportError: No module named jarabe.view.customizebundle