XML parser breaks for RHEL systems

[pramsey]

A security update to libxml2 has as a side effect changed the behaviour of the SAX1 parser when dealing with XML documents that have name spaces (which is all the XML documents we deal with, though some are XML fragments without an "ns" attribute.

​https://gitlab.gnome.org/GNOME/libxml2/-/issues/535 ​https://access.redhat.com/errata/RHSA-2024:0119

Because the OS is changing underneath us, we have no real choice except to conform our code to the new libxml behaviour. The most "future proof" way is to stop forcing use of the SAX1 parser in our code, and instead use the default parser. This slightly "modernizes" our use of libxml and hopefully avoids any further future issues that might come from our dependence on SAX1.

Fixes will have to be applied back through all versions we want to retain XML handling on RHEL systems. RHEL might eventually fix the SAX1 behaviour, but we have no idea if or when that will happen, so our change is required.

[Paul Ramsey <pramsey@…>]

In a3df807/git:

Change XML parsing to use default (SAX2) parser, references #5662

[Paul Ramsey <pramsey@…>]

In 5526b4b/git:

Change XML parsing to use default (SAX2) parser, references #5662

[Paul Ramsey <pramsey@…>]

In 173f5cf/git:

Change XML parsing to use default (SAX2) parser, references #5662

[Paul Ramsey <pramsey@…>]

In 2adb8a3b/git:

Change XML parsing to use default (SAX2) parser, references #5662

[Paul Ramsey <pramsey@…>]

In 9d49efb/git:

Change XML parsing to use default (SAX2) parser, references #5662

[Paul Ramsey <pramsey@…>]

In 299ac29/git:

Change XML parsing to use default (SAX2) parser, references #5662

[Paul Ramsey <pramsey@…>]

In ca800d25/git:

XML parser breaks for RHEL systems, references #5662