Stop repeat inference attempt causing a RuntimeError in Python3.7

[brycepg]

Empty generators and next calls within a generator without a default argument
now cause a cascade effect which results in a RuntimeError.

Raise InferenceError instead of return None to avoid the above problem.

Close pylint-dev/pylint#2317

[brycepg]

Duplicate CI tasks because I accidentally created a branch on PyCQA/astroid and then deleted

[PCManticore]

I'll check this PR these days, thanks! My main concern is why we now need to raise an inference error.

[brycepg]

because returning an empty generator would cause next calls to raise stopiteration which causes a runtimeerror in 3.7. The alternative would be to catch StopIteration on every next call inside of a generator

[PCManticore]

@brycepg The reason I was concerned is that path_wrapper should not care about the fact that in its upper call sites we're raising InferenceError to propagate an inference issue down to the consumers. But from a short look it seems that the corresponding inference methods weren't decorated at all with raise_if_nothing_inferred, which should deal with this problem at a more general level. I've pushed 8841891 which seems to fix the original problem from pylint. I merged your PR locally to get the text without the raising of the InferenceError.

[brycepg]

Alright, sounds good