Better yield condition

[kaste]

1. Currently, a yield <conditon> where the condition itself throws leaves the test in an undefined state.

E.g. yield panel.find(...) when panel is None

This PR reraises the error inside the generator (gen.throw()).

2. It is also useful and cheap to implement to get the last value back in the test. This is implemented using gen.send() instead of just next(gen)

        region = yield from lambda: panel.find(COMMIT_1, 0, sublime.LITERAL)
		# assert that region is placed correctly

3. From a tester standpoint a condition that times out must throw, currently it 'continues anyway'.

E.g. in the GitSavvy tests I often have to do

        yield from lambda: panel.find(COMMIT_1, 0, sublime.LITERAL)

        # `yield condition` will continue after a timeout so we need
        # to actually assert here
        actual = panel.find(COMMIT_1, 0, sublime.LITERAL)
        self.assertTrue(actual)

[kaste]

Okay, seems that we have test to ensure the old (3) functionality. Wonder what the rationale here is. I assumed the original author didn't know how to raise inside the generator, so that 'continue anyway' was their only option. Anyway, the first commit handles (1) and (2) and can be cherry picked. (I'm also pretty sure that my solution to timeouts (3) is the preferable behavior.)

[Thom1729]

I've been thinking of factoring out the deferred logic from UnitTesting and stealing it for sublime_lib, and I agree that this is probably the right approach.

[kaste]

Here I think we should merge this although it is technically breaking behavior. But we log a good error message.

I actually have failing conditions but passing tests while writing tests, and I think it tells me that I await the wrong thing. (Or assert the wrong thing LOL)

@randy3k WDYT?

[kaste]

Breaking is breaking and I will not push it as a 'fix/patch'. I would cherry-pick (1) and (2) and then implement (3) the breaking bit together with #146. That means (3) is then available behind a flag since we don't have sem versioning with PackageControl.