See issue #4452.
…tribute A new reference must be returned by the C getter function, not a borrowed one.
The hash value of a structured dtype was dependent on iteration order of the fields mapping, which could make (in rare conditions) two equal dtypes hash to different values. We now consider the fields in deterministic order, according to the names property. Closes #5715.
On failure, PyArray_Partition should return -1, but was returning NULL in a couple of unlikely cases.