See https://gerrit.wikimedia.org/r/c/mediawiki/extensions/GrowthExperiments/+/827549 (backport patch of an unrelated extension):
15:01:18 [0-0] Error in "For a page with eis enabled "before all" hook for "toolbar loads"" 15:01:21 Error: filetype-banned: ".djvu" is not a permitted file type. Permitted file types are png, gif, jpg, jpeg, webp, ogg, ogv, oga, flac, opus, wav, webm, mp3, midi, mid, mpg, mpeg. 15:01:21 at /workspace/src/extensions/ProofreadPage/node_modules/mwbot/src/index.js:262:31 15:01:21 at tryCatcher (/workspace/src/extensions/ProofreadPage/node_modules/bluebird/js/release/util.js:16:23) 15:01:21 at Promise._settlePromiseFromHandler (/workspace/src/extensions/ProofreadPage/node_modules/bluebird/js/release/promise.js:547:31) 15:01:21 at Promise._settlePromise (/workspace/src/extensions/ProofreadPage/node_modules/bluebird/js/release/promise.js:604:18) 15:01:21 at Promise._settlePromise0 (/workspace/src/extensions/ProofreadPage/node_modules/bluebird/js/release/promise.js:649:10) 15:01:21 at Promise._settlePromises (/workspace/src/extensions/ProofreadPage/node_modules/bluebird/js/release/promise.js:729:18) 15:01:21 at _drainQueueStep (/workspace/src/extensions/ProofreadPage/node_modules/bluebird/js/release/async.js:93:12) 15:01:21 at _drainQueue (/workspace/src/extensions/ProofreadPage/node_modules/bluebird/js/release/async.js:86:9) 15:01:21 at Async._drainQueues (/workspace/src/extensions/ProofreadPage/node_modules/bluebird/js/release/async.js:102:5) 15:01:21 at Immediate.Async.drainQueues [as _onImmediate] (/workspace/src/extensions/ProofreadPage/node_modules/bluebird/js/release/async.js:15:14) 15:01:21 at processImmediate (internal/timers.js:464:21)