Seems to be coming from wikidatawiki and commonswiki...

Change 554330 had a related patch set uploaded (by Krinkle; owner: Krinkle):
[mediawiki/extensions/Wikibase@wmf/1.35.0-wmf.8] Remove no-op 'jquery.ui.core.styles' from FullEntityParserOutputGenerator

https://gerrit.wikimedia.org/r/554330

@Krinkle I am afraid we are still seeing those errors in https://logstash.wikimedia.org/goto/dd9770ce7a81dc3c7614e03cf7b9de15

Deployments happen once a week through the train. This is expected to roll out next week with 1.35.0-wmf.10, unless backported sooner which I proposed with the above cherry pick, but not sure it'll actually happen given other priorities.

Is this a volume risk currently? In terms of MW functionality the message is harmless and the fix didn't change behavior.

Change 554330 merged by jenkins-bot:
[mediawiki/extensions/Wikibase@wmf/1.35.0-wmf.8] Remove no-op 'jquery.ui.core.styles' from FullEntityParserOutputGenerator

https://gerrit.wikimedia.org/r/554330

I deployed it in wmf.8, if everything goes well. This should be gone in a couple of hours.

Mentioned in SAL (#wikimedia-operations) [2019-12-04T19:17:11Z] <ladsgroup@deploy1001> Synchronized php-1.35.0-wmf.8/extensions/Wikibase/repo/includes/ParserOutput/FullEntityParserOutputGenerator.php: SWAT: [[gerrit:554330|Remove no-op 'jquery.ui.core.styles' from FullEntityParserOutputGenerator]] (T219604 T239594) (duration: 01m 06s)

In T239594#5712075, @Krinkle wrote:

Deployments happen once a week through the train. This is expected to roll out next week with 1.35.0-wmf.10, unless backported sooner which I proposed with the above cherry pick, but not sure it'll actually happen given other priorities.

Is this a volume risk currently? In terms of MW functionality the message is harmless and the fix didn't change behavior.

I doubt the volume would become an issue, I was under the impression that the change was in production already, mybad :)

Thank you @Krinkle and @Ladsgroup !