Backport PR #15649 on branch v2.2.4-doc (Fix searchindex.js loading when ajax fails (because e.g. CORS in embedded iframes))#15662

meeseeksmachine wants to merge 1 commit intomatplotlib:v2.2.4-docmatplotlib/matplotlib:v2.2.4-docfrom

meeseeksmachine:auto-backport-of-pr-15649-on-v2.2.4-docmeeseeksmachine/matplotlib:auto-backport-of-pr-15649-on-v2.2.4-docCopy head branch name to clipboard