Use new style cffi callbacks?

[almarklein]

https://cffi.readthedocs.io/en/latest/using.html#extern-python-new-style-callbacks

There have been reports of a specific memoryerror on MacOS M1 (see #190 and #136):

MemoryError: Cannot allocate write+execute memory for ffi.callback(). You might be running on a system that prevents this.

This looks to be a permission problem with the "old callback mechanism" that we're using. The cffi docs mention that the "new callback mechanism" does not have this problem. We only have 2 callbacks, so we might be able to fix this.

It is still a bit unclear when the error occurs - it seems to depend on a number of factors, like the Python env, conda vs pip, available brew installations, and the phase of the moon.

[almarklein]

I took a look at this, but the new-style callbacks can only be used with the API level mode, which means that cffi generates some C code that is then compiled - you need a compiler at runtime.

If we really want to we can do this, but it makes this library much less friendly to hack on. Plus I got tons of errors related to undeclared identifiers for wgu-native stuff, so I'm not even sure how well this works.

So now I really hope that there is a consistent way to prevent that memoryerror on M1 Macs 🤞

[almarklein]

I think we can conclude that our current callbacks are fine.