Comment 1 for bug 198456

The error output of the automatic upgrade tester with debug enabled:

dpkg: error processing /var/cache/apt/archives/deskbar-applet_2.21.92-0ubuntu2_i386.deb (--unpack):
 subprocess pre-installation script returned error exit status 1
+ set -e
+ which pycentral
+ pycentral --help
+ grep -q pkgprepare
+ pycentral pkgprepare deskbar-applet
Traceback (most recent call last):
  File "/usr/bin/pycentral", line 1702, in ?
    main()
  File "/usr/bin/pycentral", line 1696, in main
    rv = action.run(global_options)
  File "/usr/bin/pycentral", line 1154, in run
    runtimes = get_installed_runtimes()
  File "/usr/bin/pycentral", line 200, in get_installed_runtimes
    default_version = pyversions.default_version(version_only=True)
  File "/usr/share/pycentral-data/pyversions.py", line 139, in default_version
    if not _default_version in (debian_default, os.path.join('/usr/bin', debian_default)):
  File "/usr/lib/python2.4/posixpath.py", line 60, in join
    if b.startswith('/'):
AttributeError: 'NoneType' object has no attribute 'startswith'