Pacakage previously named python-installer in Slint, renamee python3-installer
as in SBo. We add a dummy python installer in Slint to avoid having to remove
the previous python-installer upun uinstalletion of python3 installer:
tjs way when running slapt-get upgrade python-installer will be repmaced by the
dummy package. but we also make of python3-installer a dependeny of
python-installer so that its upgrade triggers installation of
python3-installer.