BUG: Fix failing python long behaviour and possible heisen bug

The priority error fixes np.float_(64) + python_long not working
anymore. The second change reformats the
PyArray_GetAttrString_SuppressException to avoid a possible
heisenbug decrefing an object before use.

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This bugged me quite a lot... it does *not* fix the buffer error in the tests. @m-d-w did you look at that?