Bug report

Bug summary

set_aspect does not work for 3D surface plots

Expected outcome

If a sphere is drawn with plot_surface then it should appear as a sphere and not an ellipse that depends on the window sizing. This was achieved in mpl 3.0.3 by calling
set_aspect('equal').
It is now broken in mpl 3.1.1-3.1.3 because the following was inserted in matplotlib/axes/_base.py (lines1279:1282) by the developers
if (not cbook._str_equal(aspect, 'auto')) and self.name == '3d':
raise NotImplementedError(
'It is not currently possible to manually set the aspect '
'on 3D axes')

To get set_aspect to work (correctly, I might add), I have to comment out these lines in my local version of matplotlib. A plotted sphere appears as a sphere independent of the window sizing.