test: simplify WPT.assert_throws()

[Trott]

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

Affected core subsystem(s)

test url

[Trott]

/cc @joyeecheung in case there is a subtlety I am missing

[Trott]

Hmmm...oh, I think I see, this API is dictated elsewhere so we (probably) don't want to change it even if it might otherwise make sense to change it for our narrow use in our own tests?

[Trott]

(Aside: It would be great if common.WPT could be documented in the test/README.md where the common module API is documented.)

[TimothyGu]

this API is dictated elsewhere so we (probably) don't want to change it even if it might otherwise make sense to change it for our narrow use in our own tests?

Yeah, making this kind of subtle changes makes importing tests more difficult. Check out @joyeecheung's explanation (#11079 (comment)) for how WPTs are imported.

[Trott]

(Minimal doc stub for common.WPT here: #11127 If someone wants to do something more complete and informative, by all means, close that PR and open a better one.)

[Trott]

OK, makes sense to me. I'll close this.