Problem with cython-generated code: cython_function_or_method' is not an acceptable base type

[mattip]

There are problems with cython generated code that turn up when importing SciPy. This affects any feedstock that is using SciPy.

I think the problem is the seires of patches I applied after the 7.3.12 release to better support multi-phase c-extension initialization. I have further fixes on the upstream PyPy code, and will make a 7.3.13 release to re-synch the feedstock with those fixes.