Couldn't use numpy arrays as defaults on attrs 19.2

[igortg]

The following code stops working when upgrading from attrs 19.1 to 19.2:

@attr.s(auto_attribs=True)
class NumParams:
    N = 3
    alpha = np.zeros((N, Ng))

Seems that change #556 requires that default attributes should implement __eq__, which is not the case for numpy arrays.

Taceback is:

    @attr.s(auto_attribs=True)
../../../../miniconda/envs/attests/lib/python3.6/site-packages/attr/_make.py:1010: in wrap
    return builder.build_class()
../../../../miniconda/envs/attests/lib/python3.6/site-packages/attr/_make.py:498: in build_class
    return self._patch_original_class()
../../../../miniconda/envs/attests/lib/python3.6/site-packages/attr/_make.py:512: in _patch_original_class
    and getattr(cls, name, _sentinel) != _sentinel
E   ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

[RonnyPfannschmidt]

the issue can be resolved by switching the sentinel check from equality to is

[nicoddemus]

Yep, opening a PR right away

[hynek]

FYI 19.3.0 with that fix is on PyPI. Sorry for the regression and thanks to @RonnyPfannschmidt and @nicoddemus for the quick fix while I was sound asleep! :)