API Changes for 3.0.1
=====================

`.tight_layout.auto_adjust_subplotpars` can return ``None`` now if the new
subplotparams will collapse axes to zero width or height.  This prevents
``tight_layout`` from being executed.  Similarly
`.tight_layout.get_tight_layout_figure` will return None.

To improve import (startup) time, private modules are now imported lazily.
These modules are no longer available at these locations:

- ``matplotlib.backends.backend_agg._png``
- ``matplotlib.contour._contour``
- ``matplotlib.image._png``
- ``matplotlib.mathtext._png``
- ``matplotlib.testing.compare._png``
- ``matplotlib.texmanager._png``
- ``matplotlib.tri.triangulation._tri``
- ``matplotlib.tri.triangulation._qhull``
- ``matplotlib.tri.tricontour._tri``
- ``matplotlib.tri.trifinder._tri``