main/py3-cffi: upgrade to 1.15.0
https://cffi.readthedocs.io/en/latest/whatsnew.html#v1-15-0
Ignored test suite is failing the same tests as previous version
https://cffi.readthedocs.io/en/latest/whatsnew.html#v1-15-0
Ignored test suite is failing the same tests as previous version