Return -1 and set an exception on error; return 0 if the iterator is
exhausted, and return 1 if the next item was fetched successfully.
Prefer this API to PyIter_Next(), which requires the caller to use
PyErr_Occurred() to differentiate between iterator exhaustion and errors.
Co-authered-by: Irit Katriel <iritkatriel@yahoo.com>
Split abstract.c and float.c tests of _testcapi into two parts:
limited C API tests in _testlimitedcapi and non-limited C API tests
in _testcapi.
Update test_bytes and test_class.
Cover all the Mapping Protocol, almost all the Sequence Protocol
(except PySequence_Fast) and a part of the Object Protocol.
Move existing tests to Lib/test/test_capi/test_abstract.py and
Modules/_testcapi/abstract.c.
Add also tests for PyDict C API.