Investigate possible race condition in puppeteer helpers' request handling

[romaricpascal]

What

We've been getting a couple of 'Request is already handled!' errors during our tests. Those are intermitent and seem to happen from this custom request handler not checking that the request has already been handled before trying to answer itself.

Would be good to understand if we need to add a check that the request has already been handled before doing anything, or if something else is afoot.

Why

Make our tests more robust and reduce uncertainty

Who needs to work on this

Developers

Who needs to review this

Developers

Done when

• Cause for the 'Request is already handled!' errors has been identified
• Fix for the error has been implemented