Per https://integration.wikimedia.org/ci/job/mwext-MathSearch-testextension-zend/203/console
MathMathMLTest::testPmmlInput
Failed to render with error:<strong class='error texerror'>Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("<p>There was a problem during the HTTP request: 500 Internal Server Error