CB: See if I can get around this build failure by using Amy's new code

package.json

@@ -41,7 +41,8 @@
     "federalist": "npx gulp build",
     "lint": "npx gulp lintJS lintSass && npm run prettier:scss",
     "prestart": "npx gulp build",
-    "proof": "bundle exec htmlproofer --enforce-https=false --allow-missing-href=true --ignore-status-codes 0,403,429,503,302 --swap-urls 'https\\://designsystem.digital.gov/:/' --ignore-urls '/github.com/uswds/uswds/issues/' --ignore-files '/whats-new/updates/(2017|2018|2019|2020|2021)/,/documentation/code-guidelines/' ./_site",
+    //"proof": "bundle exec htmlproofer --enforce-https=false --allow-missing-href=true --ignore-status-codes 0,403,429,503,302 --swap-urls 'https\\://designsystem.digital.gov/:/' --ignore-urls '/github.com/uswds/uswds/issues/' --ignore-files '/whats-new/updates/(2017|2018|2019|2020|2021)/,/documentation/code-guidelines/' ./_site",
+    "proof": "bundle exec htmlproofer --enforce-https=false --allow-missing-href=true --only_4xx --ignore-status-codes 403,429 --swap-urls 'https\\://designsystem.digital.gov/:/' --ignore-files '/whats-new/updates/(2017|2018|2019|2020|2021)/,/documentation/code-guidelines/' ./_site",
     "serve": "npm run build:all-assets && bundle exec jekyll serve --drafts --future --incremental --livereload --host=localhost",
     "serve:package": "npm run build:uswds && npm run serve",
     "serve:local": "export LIBRARY_BASE_URL=\"http://localhost:3000\" && npm run serve",