We have optional tests that make use of these packages, for example:

sage: a.show(format="webm", iterations=1)  # optional -- ffmpeg

sage: with open(td + 'wave.gif', 'rb') as f: print(b'!\xf9\x04\x08\x14\x00' in f.read())  # optional -- ImageMagick

These tests are run whenever the corresponding "feature" is available, but the feature checks look only for the convert and ffmpeg programs. Both imagemagick and ffmpeg can be built without support for (say) webm files, making the tests above fail. To avoid spurious failures, the features should test for the necessary file format support, likely in the is_functional() method.

CC: @seblabbe

Component: packages: optional

Author: Sébastien Labbé

Branch: 1678c7f

Reviewer: Julian Rüth, Michael Orlitzky

Issue created by migration from https://trac.sagemath.org/ticket/33092