this bug is duplicated by #970430, from which i learned that the
unversioned packages are indeed supposed to be deleted (see also
#937695).
this resolution appears satisfactory:
--\ Remove the following packages:
libpython-dev
libpython-stdlib
python-dev
python-minimal
python
--\ Install the following packages:
python-dev-is-python2
python-is-python2
however, that's not what apt or aptitude will propose by default, so the
upgrade experience is anything but optimal. not quite as bad as #970375,
though. ;-)
