ubiquity-dm should set the metacity gconf key to turn on compositing

This bug was fixed in the package ubiquity - 2.11.0

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ubiquity (2.11.0) quantal; urgency=low

  [ Colin Watson ]
  * Install oem-config-slideshow-ubuntu in a separate pass from
    oem-config-$frontend and ubiquity-frontend-$frontend, since it may be
    missing from images; and only do this for the GTK frontend in any case,
    since other frontends don't currently use the slideshow (LP: #987050).
  * Re-enable alpha warning for quantal.
  * Upgrade to debhelper 9 for improved handling of compiler flags. Make
    sure that /usr/lib/girepository-1.0/ stays where it's supposed to be
    despite changes in the default libdir for multiarch.
  * Port to Python 3:
    - Use Python 3-style print functions.
    - Use "except Exception as e" syntax rather than the old-style "except
      Exception, e".
    - Use reduce from functools rather than relying on the builtin.
    - Use list comprehensions rather than filter or map.
    - Use open() rather than file().
    - Import configparser rather than ConfigParser if available.
    - Use input() rather than raw_input() when running under Python 3.
    - Use set comprehensions.
    - Import quote from urllib.parse rather than urllib if available.
    - Use new-style octal literals.
    - Use test.support rather than test.test_support if available.
    - Add --python2 and --python3 options to tests/run to force running the
      tests under Python 2 or 3 respectively.
    - Handle renaming of __builtin__ to builtins in Python 3.
    - Only pass unicode=1 to gettext.install in Python 2.
    - Port ubiquity.auto_update to python-apt 0.8 progress classes.
    - Use Python 3 names for itertools.izip and itertools.izip_longest if
      available.
    - Use helpers from the six module to deal with some bytes/unicode
      differences.
    - As a general rule, open subprocesses with universal_newlines=True when
      expecting to read text from them. This has no effect on Python 2
      (aside from \r\n conversion and the like, which is mostly a no-op for
      us), but causes Python 3 to read str rather than bytes. The
      exceptions at the moment are: debconf-copydb subprocesses, which
      return mixed-encoding data that needs to be handled specially; and
      when feeding the output of a subprocess to hashlib.
    - Use six.reraise rather than the three-argument form of raise.
    - Adjust test_filteredcommand for Python 3 text handling.
    - Fix test_ubi_partman.question_has_variables to handle templates files
      as binary data, since they're mixed-encoding.
    - Cope with assertItemsEqual/assertCountEqual naming difference between
      Python 2.7 and 3.2.
    - Rearrange ubiquity.i18n.get_translations to treat debconf-copydb
      output as binary data and do field-dependent decoding.
    - Adjust test_misc and test_upower to cope with file type changes in
      Python 3.
    - Use xml.etree.cElementTree instead of libxml2; it's faster, has a
      smaller footprint by virtue of being built into the standard library,
      arguably easier to read, and works with Python 3.
    - Fix a slew of file handle leaks, including making much more liberal
      use of context managers.
   ...