how to set internal server error page in gatsby
To add a 500 page create a page whose path matches the regex ^/?500/?$ (/500/, /500, 500/ or 500), most often you’ll want to create a React component page at src/pages/500.js.
Users will see the 500 error page when runtime errors happen in the getServerData function of your page.
Gatsby ensures that your 500 page is built as 500.html. Gatsby Cloud supports displaying this custom 500 page. If you’re hosting your site another way you’ll need to set up a custom rule to serve this file for 500 errors.
When developing using gatsby develop, you can still preview your 500 page by going to localhost:8000/500.