For a little while now, the Stylesheets task on teijenkins.hcmc.uvic.ca has been showing as unstable, because of this warning:

Warning: XML resolver not found; external catalogs will be ignored

SPQR found the solution: my /var/lib/jenkins/hudson-log-parse-rules file was out of date. The most recent version in SVN has a line suppressing that warning. This seems to be the fix:

cd /var/lib/jenkins
sudo svn export https://tei.svn.sourceforge.net/svnroot/tei/trunk/P5/Utilities/hudson-log-parse-rules
sudo chown jenkins hudson-log-parse-rules

Running a build right now to see if it's fixed.