Removal of `matplotlib.cm.get_cmap` in Matplotlib 3.11.0

[thehrh]

Source: Matplotlib 3.11.0 release notes (11 June 2026), which also explains how to substitute it

Problem: The method in question is used 3x by Map.plot() and results in:

AttributeError: module 'matplotlib.cm' has no attribute 'get_cmap'

This is unfortunately not covered by any tests. The latest workflow to run on master already used the 3.11.0 release.

As a result, the Docker image for PISA 4.3a1 is also affected.

[thehrh]

According to my research, the suggested substitute for matplotlib.cm.get_cmap(name)—matplotlib.colormaps[name]—was an addition to matplotlib 3.5. That release already dates back to 15 Nov 2021.

Therefore, I am going to attempt the fix above and simultaneously raise the lower bound on matplotlib from 3.0 to 3.5.