pandas started testing against Python 3.10 dev. We use pip install git+https://github.com/numpy/numpy.git to install NumPy in the CI. NumPy built successfully on Python 3.10.alpha.7, but it started failing on Python 3.10.beta.1, which was released yesterday.

CI link: https://github.com/pandas-dev/pandas/runs/2502353399

xref pandas-dev/pandas#41313