In response to https://bugzilla.suse.com/show_bug.cgi?id=1170886 YaST has
updated the RelaxNG schemas for its control.xml and autoinst.xml files:
yast2-installation-control-4.3.0
https://github.com/yast/yast-installation-control/pull/96
autoyast2-4.3.0 https://github.com/yast/yast-installation-control/pull/96

On Tumbleweed things are fine with libxml2-2.9.10 but on Leap 15.2,
libxml2-2.9.7 has a bug which fails the build of yast2-installation-control
with errors like

[   65s] ../control/control.rng:47: element attribute: Relax-NG parser error :
Found anyName attribute without oneOrMore ancestor
[   65s] Relax-NG schema ../control/control.rng failed to compile

This will not hit users of SLE15-SP2/Leap 15.2 because the above packages went
to Tumbleweed only, but it will be a problem for us developers and later 15.3
users.

Fortunately there is a workaround in rephrasing the schema file, will update
the schemas.