This change has not been advertised and cause random extensions
to start failing giving little clue to users.
Please have this change discussed on wikitech-l and announced
ahead of time to minimize disruptions. It brokes MathSearch at least:
https://gerrit.wikimedia.org/r/#/c/189442/
This reverts commit
d333cd8f7be190d7e296721caa79478ab7ef1b20.
Change-Id: If9a28b1386fca946d8ba351c16134cdf7da8a148