refactoring of exception raising code, simpler/faster/correcter code for reraising exceptions, separate implementation for Py3, minor fixes for error cases
refactoring of exception raising code, simpler/faster/correcter code for reraising exceptions, separate implementation for Py3, minor fixes for error cases

bhy/cython-haoyu,bhy/cython-haoyu,bhy/cython-haoyu,bhy/cython-haoyu