Fix pytest failure without numba.

[sebastic]

The Debian package needs to be built without numba cause llvmlite is buggy.

[ml31415]

Hello @sebastic I'd be fine merging that request. Nevertheless, I'd like to note that without the numba implementation, this package is not much more than some syntax candy around inbuilt numpy operations. So without numba available, I'm not sure if it would be worth packaging this package at all.

[sebastic]

numpy-groupies is a dependency of flox which in turn is a dependency of sarsen, having these back in the upcoming stable release is more important. If/when numba/llvmlite get fixed during the next development cycle its use in numpy-groupies can be reinstated.