Cucumber test reports sometimes cannot be viewed on Jenkins: Gateway Time-out

Originally created by @intrigeri on #12528 (Redmine)

e.g. https://jenkins.tails.boum.org/view/RM/job/test_Tails_ISO_feature-stretch/lastFailedBuild/cucumberTestReport/

What recent change can possibly have broken this?

Related issues

• Blocks tails/sysadmin#13233