It turns out I'd been on 0.9.30 before 0.9.34, so I went back to that version, and it worked. I then incrementally installed 0.9.31, 32, 33, and 34, trying the download at each step. Each succeeded, including the latest.
I suspect that what happened was one of these:
- Jumping from 0.9.30 to 0.9.34 introduced a subtle problem
- Installing two different versions of 0.9.34 introduced a subtle problem (I had started with the original 0.9.34 and then gotten the new one to fix the "no attribute" problem)
- There was cruft of some kind in my install directory. Since I had to completely uninstall to go back from 0.9.34 to 0.9.30, that cleared the cruft and fixed it for me.
Regardless, I'm working now, so from a practical perspective, it doesn't really matter to me what went wrong. Thanks for the tip to downgrade!