Porting wptserve handlers to Python 3: next steps / code review

Hello everyone,

We're getting close to finalizing the plan for migrating close to 500
wptserve handlers we have in WPT. Now we have a few concrete steps to take:

1. Regarding the trial PR
<https://github.com/web-platform-tests/wpt/pull/23363>, James, Anne and
others who'd like to take a look, do you have any other comments on this
PR, especially high-level ones about the general approach? This would
unblock the following steps and we can address small issues in parallel.
2. If we agree this approach is what we wanted by having consistent and
explicit semantics across Python 2 and 3, I'll update the RFC
<https://github.com/web-platform-tests/rfcs/pull/49> (essentially swapping
the currently "recommended" and "alternative" approaches and filling in
some more concrete guidelines), and kick off a new round of RFC process
(hopefully relatively quick since many people are already on board with the
new approach).
3. Meanwhile, Ziran can start porting more handlers (we can wait until the
RFC is accepted to actually merge the PRs). We have hundreds of handlers
and we should expect lots of PRs. Reviewing them is a critical task, too.
Since we now have concrete guidelines and changes will be largely
mechanical, I'm proposing to adopt the "LGTM % nits" convention widely used
in Chromium: if a PR largely looks good but has some minor issues, approve
the PR with comments. In addition, we'd really appreciate a few more people
to sign up for reviewing these changes to share the workload. Anyone
volunteering?

Best,
Robert