Boolean array indices with mismatching shapes now properly give ``IndexError``
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Previously, if a boolean array index matched the size of the indexed array but
not the shape, it was incorrectly allowed in some cases. In other cases, it
gave an error, but the error was incorrectly a ``ValueError`` with a message
about broadcasting instead of the correct ``IndexError``.

For example, the following used to incorrectly give ``ValueError: operands
could not be broadcast together with shapes (2,2) (1,4)``:

.. code:: python

   np.empty((2, 2))[np.array([[True, False, False, False]])]

And the following used to incorrectly return ``array([], dtype=float64)``:

.. code:: python

   np.empty((2, 2))[np.array([[False, False, False, False]])]

Both now correctly give ``IndexError: boolean index did not match indexed
array along dimension 0; dimension is 2 but corresponding boolean dimension is
1``.