<img src="#x"> crashes the builder

[peterbe]

Put this into a HTML page:

<img src="#x">

This is what happens if you try to view the page:

2:49:18 PM server.1     |  Error in buildDocumentFromURL(/en-us/docs/web/api/window/personalbar/) Error: The document's slug (Web/API/Window/personalbar) doesn't match its disk folder name (en-us/web/api/window/personalbar/)
2:49:18 PM server.1     |      at buildDocument (/Users/peterbe/dev/MOZILLA/MDN/yari/build/index.js:220:11)
2:49:18 PM server.1     |      at buildDocumentFromURL (/Users/peterbe/dev/MOZILLA/MDN/yari/server/index.js:52:16)
2:49:18 PM server.1     |      at /Users/peterbe/dev/MOZILLA/MDN/yari/server/index.js:220:25
2:49:18 PM server.1     |      at Layer.handle [as handle_request] (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/express/lib/router/layer.js:95:5)
2:49:18 PM server.1     |      at next (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/express/lib/router/route.js:137:13)
2:49:18 PM server.1     |      at Route.dispatch (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/express/lib/router/route.js:112:3)
2:49:18 PM server.1     |      at Layer.handle [as handle_request] (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/express/lib/router/layer.js:95:5)
2:49:18 PM server.1     |      at /Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/express/lib/router/index.js:281:22
2:49:18 PM server.1     |      at param (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/express/lib/router/index.js:354:14)
2:49:18 PM server.1     |      at param (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/express/lib/router/index.js:365:14)

This is what happens when you try to yarn build a HTML file that contains that:

▶ yarn build /Users/peterbe/dev/MOZILLA/MDN/content/files/en-us/web/api/window/personalbar/index.html
yarn run v1.22.10
$ cross-env NODE_ENV=production node build/cli.js /Users/peterbe/dev/MOZILLA/MDN/content/files/en-us/web/api/window/personalbar/index.html

Building Documents...
Building roots: [ '/Users/peterbe/dev/MOZILLA/MDN/content/files' ]
Building roots: [ '/Users/peterbe/dev/MOZILLA/MDN/content/files' ]
Error: ENOTSUP: operation not supported on socket, copyfile '/Users/peterbe/dev/MOZILLA/MDN/content/files/en-us/web/api/window/personalbar/' -> '/Users/peterbe/dev/MOZILLA/MDN/yari/client/build/en-us/docs/web/api/window/personalbar/personalbar'
    at Object.copyFileSync (node:fs:2016:3)
    at buildDocuments (/Users/peterbe/dev/MOZILLA/MDN/yari/build/cli.js:185:10)
    at processTicksAndRejections (node:internal/process/task_queues:93:5)
    at async Se._action (/Users/peterbe/dev/MOZILLA/MDN/yari/build/cli.js:286:60)
    at async Se.run (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/@caporal/core/dist/index.js:1:27579)
    at async Te._run (/Users/peterbe/dev/MOZILLA/MDN/yari/node_modules/@caporal/core/dist/index.js:1:32257) {
  errno: -45,
  syscall: 'copyfile',
  code: 'ENOTSUP',
  path: '/Users/peterbe/dev/MOZILLA/MDN/content/files/en-us/web/api/window/personalbar/',
  dest: '/Users/peterbe/dev/MOZILLA/MDN/yari/client/build/en-us/docs/web/api/window/personalbar/personalbar'
}

error: ENOTSUP: operation not supported on socket, copyfile '/Users/peterbe/dev/MOZILLA/MDN/content/files/en-us/web/api/window/personalbar/' -> '/Users/peterbe/dev/MOZILLA/MDN/yari/client/build/en-us/docs/web/api/window/personalbar/personalbar'

error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.