07:55:15 PHP Deprecated: Comments starting with '#' are deprecated in /etc/php5/cli/conf.d/fss.ini on line 1 in Unknown on line 0
Looks like this isn't specific to Continuous Integration slaves, probably some generic php/webserver module that Wikimedia or Ubuntu provides that needs updating.
[0] https://integration.wikimedia.org/ci/job/php-composer-validate/6/console
Version: wmf-deployment
Severity: minor
I have fixed it in July 2013 with https://gerrit.wikimedia.org/r/#/c/76511/ , bumping php-fss to 1.0-2 but it is not deployed.
RT #7213 asked to have it uploaded but it is blocked because some new commit introduce HHVM supports which might be breaking change.
Beside the annoying warning message, that does not cause that much havoc so lowering priority.
The new php5-fss package has been build and uploaded on apt.wikimedia.org for Precise. It was already up to date for Trusty.
I have upgraded the package on: