quickplot.contourf colorbar not attached to supplied axes

[rcomer]

🐛 Bug Report

Following on from #2946, when the axes labels were fixed. I just noticed that quickplot.contourf still attaches the colorbar to the current axes, even if a different axes is supplied.

How To Reproduce

import matplotlib.pyplot as plt
import iris
import iris.quickplot as qplt

fig1 = plt.figure()
fig2 = plt.figure()

fname = iris.sample_data_path('hybrid_height.nc')
theta = iris.load_cube(fname, 'air_potential_temperature')
cross_section = next(theta.slices(['grid_longitude',
                                   'model_level_number']))

ax = fig1.add_subplot(2, 1, 1)
qplt.contourf(cross_section, axes=ax)

plt.show()

Fig 1:

Fig 2:

Expected behaviour

Colorbar should be attached to the axes containing the contour plot.

Environment

• OS & Version: RHEL 7.9
• Iris Version: 3.1.dev0

[rcomer]

With latest matplotlib, the above code produces this warning:

MatplotlibDeprecationWarning: Starting from Matplotlib 3.6, colorbar() will steal space from the mappable's axes, rather than from the current axes, to place the colorbar.  To silence this warning, explicitly pass the 'ax' argument to colorbar()

So it rather looks like this issue will be fixed for us.

[rcomer]

Done in #4894