Log Message:
py-cppy: update to 1.2.1.

1.2.1 - 03/30/2022
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- make the pyproject.toml fully PEP 621 compliant PR #19

1.2.0 - 03/11/2022
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- expose a build_ext subclass that can be re-used in other projects PR #16
- use a PEP 517 compatible install procedure PR #16
- do not access directly ob_type on PyObject use Py_TYPE