Investigate bug with nevergrad 0.3

[mstimberg]

After updating nevergrad to version 0.3, our test suite fails: https://travis-ci.org/brian-team/brian2modelfitting/jobs/638442404

It fails with an error in the "instrumentation" code:

    def _check_shape(self, x: np.ndarray) -> None:

        if self.shape != (1,) and x.shape != self.shape:

>           raise ValueError(f"Shapes do not match: {self.shape} and {x.shape}")

E           ValueError: Shapes do not match: () and (1,)

../../../virtualenv/python3.6.7/lib/python3.6/site-packages/nevergrad/instrumentation/transforms.py:127: ValueError

I did not look in detail, but I think it expects a scalar where we provide a length-1 array (or the other way around).

[mstimberg]

Closed via 617e8b9 and ed6e426.