> In conversation with Dan, I have fixed my conda package (but overwritten the same version).  I needed to add this to the build:
> # sudo apt-get install gcc-multilib
> CC='gcc -m32' make python

Thanks. That fixes it for me as well. I never even looked at intobject.c, since it compiled out of the box, and didn't dig into it when I saw the error. Looking now, I see a 32-bit assumption:

if (x > 0x7fffffff || x < (double) (long) 0x80000000)
    return err_ovf();

With the -m32 flag, running lib/testall.py runs to completion.