In the interest of getting 3.3.1 out, we skipped the test_interactive_backend test on Travis macOS. It works correctly on a 'real' macOS machine from MacStadium, so we were okay with this for now. However, we should get to the bottom of this failure, whether it's because of old macOS settings on Travis, or whether it's something we can't rely on overall.

Matplotlib version

• Operating system: macOS
• Matplotlib version: master+Go back to checking figures for their manager in destroy. #18184 (45d748b)
• Matplotlib backend (print(matplotlib.get_backend())): macOS
• Python version: 3.8.5

Marked as Good first issue, as this should be self-contained to the macOS backend and CI, but Medium difficulty, because it's CI...