python2.6's internal xml parser is not enough for gla11y, but it can run
python-lxml fine.

Change-Id: I725471729c8e2f25ce60f1d92e08d87a96e171a5
Reviewed-on: https://gerrit.libreoffice.org/50686Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>