test_never_update is flaky #18246
Description
Bug report
So far, I've only seen this on macOS CI. test_never_update crashes and thus fails.
On #18235, I had to restart macOS on Azure 4 times to pass. In #18243 it failed on Travis and Azure, but only macOS.
Matplotlib version
- Operating system: macOS, mostly
- Matplotlib version: master-ish
- Matplotlib backend (
print(matplotlib.get_backend())): TkAgg - Python version: 3.7.8 / 3.8.5