PR Summary

If an axes is hidden (set_visible(False)) then it has no tightbbox. But we still need to position it w/ constrained_layout, pointed out in #14917 (thanks @ImportanceOfBeingErnest )

Closes #14918

import numpy as np
import matplotlib.pyplot as plt

fig5, axs = plt.subplots(2, 2, constrained_layout=True)
axs[0,1].set_visible(False)
plt.show()

PR Checklist

• Has Pytest style unit tests
• Code is Flake 8 compliant
• New features are documented, with examples if plot related
• Documentation is sphinx and numpydoc compliant
• Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
• Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way