Drop testtools support?

[vytas7]

At the time of writing, our documentation might give an impression that using testtools is the preferred way to write tests for a Falcon app.

I haven't done any research or survey in the area, but just subjectively it feels that the most popular testing frameworks in 2023 are pytest followed by the stdlib's unittest (both are also well supported by Falcon).
Moreover, IIRC I had to exclude testtools from our test dependencies when adding Python 3.10 CI gates, since it wasn't 3.10-ready by the time. So it's becoming a maintenance burden, too.

OTOH, it seems that there has been a new testtools release, and the project is still maintained. So after all maybe it doesn't hurt to keep the integration?

Even if we decide to keep testtools, we should IMHO reword the docs not to give the impression it is the preferred way, and link to our tutorial for using pytest in the same paragraph.

[vytas7]

Another option is to drop testtools, but leave an escape hatch via an envvar along the lines of Custom HTTP Methods if anyone is still using that.

[CaselIT]

I have no opinion on this, either way works for me

[kgriffs]

I don't think we need to keep supporting it. It's a minor convenience left over from early OpenStack days for a very small community relative to the broader python ecosystem.