[Installit-dev] XML validation

[Jannis Pohlmann]

Hey all,

I worked on Parsers for the mirror list and the package list last days.
I tried to replace DTD validation by a "smarter" solution which just
skipped invalid mirrors/packages/groups etc. But this makes the code
almost unreadable (even if you move logging messages etc. into separate
methods) so I suggest we should at least depend on PyXML
(http://pyxml.sf.net). It's the most common XML toolkit for Python and
should be available for all platforms.

We'll be doing heavy XML parsing/writing stuff and we need to perform
proper validation in order to detect errors in the XML formats as early
as possible.

Another idea would be to just rely on the mirror maintainers/packagers
to provide valid file and just raise Exceptions if something's not correct.

What do you think about it?

- Jannis