BUG: pytables in py39
There are failures I'm getting locally since homebrew bumped up to py39.  I'm not seeing them on the CI, but they _did_ appear around the same time as these [different](https://dev.azure.com/pandas-dev/pandas/_build/results?buildId=48423&view=logs&j=2d7fb38a-2053-50f3-a67c-09f6e91d3121&t=449937cc-3d50-56b5-5662-e489f41f1268) unexplained pytables failures started showing up.