Traceback (most recent call last):
  File "/usr/bin/sugar-install-bundle", line 21, in <module>
    bundle = ActivityBundle(name)
  File "/usr/lib/python3.7/dist-packages/sugar3/bundle/activitybundle.py", line 118, in __init__
    info_file = self.get_file('activity/activity.info')
  File "/usr/lib/python3.7/dist-packages/sugar3/bundle/bundle.py", line 126, in get_file
    f = six.StringIO(data)
TypeError: initial_value must be str or None, not bytes

Fix by always reading bundle and metadata as Bytes, and converting to
String before passing to ConfigParser.

Did not fix ContentBundle, as it has been unused for some time, and was
only kept for use with OLPC XO and Python 2.