fix XML validation error

[tomkralidis]

Description

As per #453, XML validation fails when using lxml >=3.6.3.

Environment

• operating system: ubuntu trusty
• Python version: 2.7
• pycsw version: master
• source/distribution
  • git clone
  • DebianGIS/UbuntuGIS
  • PyPI
  • zip/tar.gz
  • other (please specify):
• web server
  • Apache/mod_wsgi
  • CGI
  • other (please specify):

Steps to Reproduce

See #453 test results.

Additional Information

The issue is rooted either in lxml or libxml2: https://mailman-mail5.webfaction.com/pipermail/lxml/2016-August/007757.html

[tomkralidis]

Turns out it's a libxml2 error in 2.9.4. 2.9.3 works.

[kalxas]

Lets keep this open for reference by external projects

[tomkralidis]

+1. Associated bug report, test case, and patch.

[tomkralidis]

@kalxas this is now resolved/fixed upstream. Wondering if these fixes have made it to packaging?

[kalxas]

I see that libxml2 released 2.9.7 few days ago.
@tomkralidis which is the upstream release that included that fix? The last one?

[kalxas]

https://github.com/GNOME/libxml2/blob/72182550926d31ad17357bd3ed69e49d7e69df02/doc/news.html#L258
so it was 2.9.4 that fixed this issue

[kalxas]

Debian 9.0: libxml2 2.9.4+dfsg1-2.2+deb9u1
Ubuntu Xenial: libxml2 2.9.3+dfsg1-1
Ubuntu Bionic: libxml2 2.9.4+dfsg1-5ubuntu1
Redhat EL 7 / CentOS: libxml2 2.9.1-6.el7_2.3
openSUSE Leap 42.3: libxml2-2.9.4-12.1

Current Ubuntu LTS, RedHat/CentOS 7 and Debian 8.0 (old stable) still have the old libxml version.

[tomkralidis]

@kalxas can we close? Perhaps enough time has gone by where newer versions of libxml2 are now widespread.

[kalxas]

Debian 9.0: libxml2 2.9.4+dfsg1-2.2+deb9u2
Debian 10.0: libxml2 2.9.4+dfsg1-7+b3
Ubuntu Xenial: libxml2 2.9.3+dfsg1-1ubuntu0.6
Ubuntu Bionic: libxml2 2.9.4+dfsg1-6.1ubuntu1.2
RedHat EL 7/CentOS: libxml2 2.9.1-6.el7_2.3
RedHat EL 8: not known yet
openSUSE Leap 15.0: libxml2 2.9.7
openSUSE Leap 15.1: libxml2 2.9.7