The current last update of kiwi in Leap15.1 does not include python2 support.
Since there is no more python2 support for kiwi 9.18.x series the
`update-alternatives` dependency that was handling the default kiwi version
(py2 or py3) in use is no longer included. The result of that is python2-kiwi
and latest python3-kiwi should not coexist both in the system as they have non
coordinated and overlapping use of symlink such as `/usr/bin/kiwi` and
`/usr/bin/kiwi-ng`.

My approach to solve that would be including an `Obsoletes: python2-kiwi` and
`Conflicts: python2-kiw` in python3-kiwi package. This way we ensure both
versions are not present in the system.

@Ludwig would this solution be acceptable to you?